CHEMICAL  ASPECTS  OF 
SILK  MANUFACTURE 


RNBACH 


liiii  illil  1H  iiiiil 


i 


THE    CHEMICAL  ASPECTS 


OF 


SILK  MANUFACTURE 


BY 


R.  LIVINGSTON  ,FERNBACH,  Sc.D. 

Technical  Advisor  of  the  Chemico-Legal  Bureau,  New  York  City;  Expert 

in  Techno-Legal  Practice;  Consulting  Chemist  to  the  Silk  Trade; 

Author  of  "Glues  and  Gelatine,  a  Practical  Treatise 

on  their  Testing  and  Use" 


NEW   YORK 

THE    AUTHOR 

1910 


Copyright,  1910,  by 
R.  LIVINGSTON   FERNBACH 


The  Plimpton  Press  Norwood  Mass.  U.S. A. 


PREFACE 

FIVE  years  ago,  Mr.  Hollins  Rayner,  in  his  admirable 
work,  "Silk  Throwing  and  Waste  Silk  Spinning,"  gave 
to  the  trade  the  first  practical  account  of  the  production 
of  a  weavable  thread  from  the  fiber  of  the  silkworm. 
De  L'Arbousset,  Edwards,  von  Georgeviecs,  Hurst,  Merritt 
Matthews,  and  others  have  contributed  much  of  importance 
concerning  silk,  albeit  chiefly  in  its  relation  to  the  other 
fibers,  its  culture,  or  in  the  form  of  a  compendium  of  dye- 
ing and  printing  formulas  long  since  obsolete. 

To  the  deep-rooted  fallacy  that  the  problem  of  silk 
manufacture  is  mechanical,  confined  to  the  phase  of  throw- 
ing, winding,  warping,  and  weaving,  this  book  owes  its 
existence.  In  these  pages  the  all-important  chemical 
aspects  of  the  industry  —  the  principles  which  are  the 
very  basis  of  mechanical  practice  —  are  impartially  set 
forth.  In  publishing  the  results  of  an  extended  practical 
experience,  the  author  betrays  no  confidence.  He  is 
aware  that  publications  of  this  type  arouse  the  antago- 
nism of  those  members  of  the  trade  in  whose  sight  all  efforts 
toward  enlightenment  constitute  the  unpardonable  sin. 
On  the  other  hand,  the  author  disavows  all  sympathy 
with  the  concoctors  of  catch-penny  tables,  who,  posing 
as  altruists,  are  in  reality  alarmists  seeking  self-advance- 
ment through  the  exploitation  of  exploded  theories. 

2545S9 


vi  PREFACE 

The  inauguration  of  a  new  era,  in  which  rigid  scientific 
control  supersedes  rule  of  thumb  in  silk  manufacture,  is 
at  hand.  The  writer  of  this  treatise  earnestly  hopes  that 
it  may  assist  the  manufacturer  to  a  better  understanding 
of  the  processes  to  which  his  material  is  subjected. 

R.  LIVINGSTON  FERNBACH. 

CHEMICO-LEGAL  BUREAU, 

97  Warren  Street,  N.  Y.  C. 
October,  1909. 


TABLE  OF  CONTENTS 

CHAPTER  PAGE 

I.     RAW  SILK 1 

Varieties   of   Moth.  —  Some    Phases   of   Sericulture. 

—  The    Silk   Fiber.  —  Sericin   and   Fibroin.  —  Cocoon 
Reeling. 

II.     SILK  THROWING 12 

The  Commercial  Fiber.  —  Throwing  Materials.  — 
The  Throwing  Process.  —  Clearance.  —  Influence  of 
Throwing  on  Subsequent  Operations. 

III.  SILK  STRIPPING 22 

Hardness  of  Sericin.  —  Steam  Stretching.  —  Materials 
Employed.  —  The  Process.  —  Influence  of  Water  and 
Temperature.  — Souple.  — Stripping  Tussah.  —  Fiochetti 
or  "Lousiness." 

IV.  SILK  BLEACHING        31 

Stoving.  —  The  Modern  Sulphurous  Acid  Process.  — 
Hydrogen  and  Sodium  Peroxides.  —  Bleaching  Tussah.  — 
Influence  of  Stripping  on  Bleaching. 

V.     SILK  WEIGHTING 36 

Weighted  vs.  Pure  Dye  Silks.  —  Older  Methods.  — 
The  "Dynamite"  Process. — Weighting  for  Colors.  — 
Weighting  for  Blacks.  —  Influence  of  Prior  Processes  on 
Weighting. 

VI.    SILK  DYEING        47 

Skein  Dyeing.  —  Colors.  — Blacks.  —  Fast  Colors.  — 
Developed  Colors.  —  Piece  Dyeing.  —  Influence  of  Prior 
Processes  on  Dyeing. 

VII.    SILK  PRINTING  AND  FINISHING 55 

Print  Colors.  —  Color  Thickeners.  —  Direct  Print- 
ing. —  Resist  Printing.  —  Discharge  or  Extract.  — 
Finishing  Media.  — Thread  Finishing.  — Piece  Finishing. 

VIII.     SILK  CONDITIONING 62 

Chemical  versus  Physical  Conditioning. 

APPENDIX 69 

Influence  of  Heat,  Cold,  and  Moisture  on  Winding, 
Warping,  and  Weaving.  —  Influence  of  Prior  Processes. 

—  Useful  Data. 

vii 


THE   CHEMICAL   ASPECTS   OF   SILK 
MANUFACTURE 

CHAPTER  I 
RAW   SILK 

VARIETIES  OF  MOTH.  —  It  is  estimated  that  Nature  has 
produced  from  five  hundred  to  six  hundred  varieties  of 
silk-producing  larvae.  Of  this  great  number,  however, 
only  a  few  are  of  commercial  importance;  and  chief  among 
these  is  the  Bombyx  Mori  which  derives  its  name  from  the 
circumstance  that  its  food  is  principally  the  leaf  of  the 
Morus  Alba  or  white  mulberry.  This  is  the  typical  Chinese 
moth,  producing  the  finest  grades  of  silk  hi  Italy  and  France 
as  well  as  in  China.  The  cocoons  of  the  Bombyx  are  all  of 
the  closed  variety;  that  is,  the  threads  cover  the  ends  of 
the  cocoons  without  a  break.  Its  silk  being,  therefore, 
entirely  reelable,  it  is  the  most  valuable  commercially. 

Following  in  the  order  of  importance  comes  the  Tussah 
group  of  silkworms,  of  which  the  Antheria  Mylitta,  indigent 
to  China  and  India,  is  a  characteristic  example.  The 
Mylitta  worm  is  larger  than  the  Bombyx  and  spins  a  cocoon 
of  far  greater  size.  In  comparison  with  that  of  the  Bombyx, 
its  thread  is  about  g^-g-  inch  in  diameter,  whereas  that  of 
the  latter  is  only  -igVo"  °^  an  mcn- 

The  silk  produced  by  the  Antherea  group  is  distinguished 
by  the  tenacity  and  great  resistance  of  its  coloring  matter 
to  discharging  agents.  Although  the  silk  of  the  Bombyx 
ranges  in  color  from  white  through  yellow,  to  orange,  it 
is  always  a  pale  cream,  at  worst,  after  the  gum  has  been 
boiled  off.  On  the  other  hand,  the  original  dark  color  of 

1 


:   'dH^MI€Ali  .ASPEGIB  OF  SILK  MANUFACTURE 


Tussah  is  removable  only  through  the  most  radical  bleach- 
ing treatment. 

It  is  interesting  to  note  that  the  food  on  which  the  worm 
is  reared  has  a  direct  influence  upon  the  color  of  the  silk 
spun  by  the  worm.  Thus  the  Yama  Mai,  a  Japanese 
member  of  the  family  Antlierea,  feeding  on  a  variety  of 
oak,  produces  a  greenish  cocoon,  whereas  that  of  the 
Attacus  Cynthia  of  the  Citernia  family,  which  feeds  on  ash 
leaves,  is  grayish  in  color.  When  the  Attacus  Cynthia  was 
introduced  into  India,  where  it  is  known  as  Ricini,  it  was 
reared  on  the  Castor  Oil  plant  (whence  the  latter  name) 
which  is  responsible  for  the  very  deep  yellow  color  of  the 
silks  known,  as  Rajah  or  Bengals. 

SOME  PHASES  OF  SERICULTURE.  —  We  are  apprised, 
from  time  to  time,  of  attempts  to  introduce  the  culture 
of  the  silkworm  into  the  United  States  and  it  is  to  be  noted 
that  each  attempt  thus  far  has  failed  —  although  it  has 
been  adequately  proven  that  the  climate  of  certain  sections 
of  this  country  is  well  adapted  to  the  cultivation  of  the  worm 
for  breeding  purposes.  Similarly,  certain  varieties  of  worm, 
notably  the  Antlierea  Pernyi,  an  oak-feeding  worm  indigent 
to  the  Himalayas,  have  been  successfully  reared  in  Eng- 
land. Silkworm  culture  for  breeding  purposes  is  one 
thing;  for  the  purposes  of  producing  commercial  silk,  quite 
another. 

Many  insurmountable  obstacles  preclude  successful  seri- 
culture in  the  United  States.  Not  only  is  the  high  labor 
a  factor,  but  apart  from  this  we  lack  the  necessary  experi- 
ence —  an  experience  which  has  an  empirical  rather  than 
an  exact  foundation.  Success  in  sericulture  seems  to  be 
largely  a  matter  of  intuition.  The  faculty,  for  example, 
of  preventing  the  spread  of  disease  amongst  the  worms 
at  the  psychological  moment  must  necessarily  be  inbred 
of  generations  of  practical  experience  in  the  craft, 


RAW  SILK  3 

The  great  tendency  of  the  worm  to  disease  is  indeed  the 
chief  obstacle  in  the  way  of  successful  sericulture.  The 
nursing  of  its  voracious  appetite  is  as  naught  compared 
with  the  care  necessary  to  preserve  its  health.  To  one 
gifted  with  the  remotest  sense  of  humor,  the  study  of  the 
habits  of  the  worm  is  fraught  with  endless  amusement. 
Certain  of  his  characteristics,  to  wit,  his  refusal  to  work 
unless  his  diet  is  just  so,  are  so  human  as  to  be  startling. 
In  his  general  behavior  he  is  a  hobo  in  miniature! 

The  silkworm  is  the  victim  of  five  diseases  each  permit- 
ting of  distinct  diagnosis.  Of  these  five,  Lacherie  and 
Calcino  are  the  more  important,  the  latter  being  most 
dangerous.  Lacherie  is  a  form  of  malaria.  When  stricken 
with  this  disease  the  worm  becomes  indifferent  to  its 
food  and  subsequently  spins  a  weak  and  worthless  fiber. 
The  first  symptom  of  Calcino,  as  that  of  Lacherie,  is  failure 
to  feed.  This  is  rapidly  succeeded,  however,  by  complete 
inanition  and  a  gradual  hardening  of  the  body,  when, 
after  24  hours,  it  is  covered  with  a  chalky  coating  which 
gives  to  the  disease  its  name.  Recent  research,  however, 
has  conclusively  proven  that  the  worm  is  not  " ossified" 
as  was  originally  supposed.  The  disease  has  been  traced 
to  a  parasite  of  microscopical  proportions  which  feeds  on 
the  worm,  sapping  its  vitality  with  incredible  rapidity. 
Shortly  before  death  ensues  the  spores  of  this  parasitic 
fungus  burst,  covering  the  body  of  the  worm  with  their 
chalk-like  contents. 

When  one  considers  that  disease  may  have  its  origin 
in  the  tiny  eggs,  —  the  size  of  a  pin  head  —  one  begins 
to  realize  some  of  the  difficulties  of  sericulture.  It  is  stated 
that  the  one  reliable  method  of  determining  whether  the 
eggs  are  diseased  or  not  is  to  place  them  in  boiling  water 
when,  if  they  are  in  healthy  condition,  they  acquire 
a  purplish  tint.  Unfortunately,  the  acquirement  of  the 


4      CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

favorable  hue  can  be  but  small  satisfaction  to  the  operator, 
as  the  treatment  kills  the  embryo  within  the  egg.  With 
these  facts  in  view,  it  is  the  more  marvelous  that  the 
world's  production  of  commercial  silk  totals  its  present 
amount. 

At  the  first  sign  of  disease  amongst  the  worms,  drastic 
measures  are  perforce  adopted.  Fumigation  of  the  entire 
colony  by  means  of  the  fumes  of  sulphur  is  at  once  resorted 
to.  Just  how  far  this  drastic  treatment  is  responsible 
for  deterioration  of  the  fiber  subsequently  spun  by  the 
worm  is  not  known.  Opinions  on  this  point  differ  radi- 
cally. It  is  stated  by  some  that  fumigation  is  the  ultimate 
cause  of  Fiochetti  or  true  lousiness.1  Others,  again,  hold 
the  treatment  harmless.  It  is  reasonable  to  assume,  how- 
ever, that  certain  defects  in  the  ultimate  silk  fiber  must 
ensue  from  operations  of  this  kind. 

One  of  the  important  precautions  to  be  observed  in  the 
rearing  of  silkworms  is  the  ascertaining  that  the  eggs  will 
not  hatch  before  the  food  for  the  young  worms  is  ready 
for  their  immediate  consumption.  Without  proper  sus- 
tenance the  young  worm  at  once  dies.  Rayner2  states 
that  the  frequent  reports  of  scarcity  of  silk  owing  to  frost 
are  accounted  for  in  the  fact  that  the  frost,  by  killing  the 
young  mulberry  leaves,  deprives  the  newly  hatched  worms 
of  sustenance  and  hence  they  cannot  live.  He  discounts 
these  " early  frost"  rumors  on  the  ground  that  they  are 
promulgated  by  astute  brokers  in  the  endeavor  to  create 
a  better  price  for  the  prospective  raw  silk  crop.  Be  this 
as  it  may,  scarcity  of  the  raw  product  may  be  due  to  a 
hundred  and  one  valid  causes  —  the  outcome  of  the  many 
insuperable  difficulties  encountered  in  sericulture. 

*  Divisibility  of  the  Silk  Fiber.     Sir  Thomas  Wardle,  Leek. 
2  Silk  Throwing  and  Waste  Silk  Spinning,  Hollins  Rayner  (Scott, 
Greenwood  &  Co.,  London). 


HAW   SILK 


The  relation  of  the  constitution  of  the  food  of  the  worm 
to  the  worm  itself,  and  subsequently  to  the  silk  fiber,  will 
be  better  understood  from  the  following  approximate 
analysis  of  the  mulberry  leaves  and  the  dried  worms  fed 
thereon. 


WORMS  (DRIED) 

MULBERRY  LEAF 

Mineral  matter  

9  per  cent 

12  per  cent 

Carbon        .  . 

48  per  cent 

44  per  cent 

Hydrogen  

7  per  cent 

6  per  cent 

Nitrogen  
Oxvffen.  . 

10  per  cent 
26  per  cent 

3  per  cent 
35  per  cent 

It  is  readily  inferred  from  these  figures  that  any  change 
in  the  constitution  of  the  leaves,  through  blight,  frost,  or 
other  factor  adverse  to  proper  growth,  must  necessarily 
bring  about  a  corresponding  change  in  the  constitution  of 
the  worm  and  ultimately  in  the  fiber  it  spins.  Indeed, 
the  influence  of  diet  on  the  character  of  the  product  of  an 
animal  organism  is  not  confined  to  the  case  of  the  silk- 
worm. Thus,  the  oil  extracted  from  the  lard  of  corn-fed 
hogs  is  of  different  character  from  that  extracted  from  the 
lard  of  swill-fed  hogs.  The  latter  oil  is  whiter  in  color 
and  exhibits,  as  a  rule,  less  initial  free  fatty  acids  than  the 
former  and  is  far  more  easily  "refined"  —  all  this  assuming 
that  the  extraction  and  refining  process  are  alike  in  both 
instances. 

The  purpose  of  the  above  limited  discussion  of  seri- 
culture is  to  impress  upon  the  reader  the  fact  that  many 
variations  in  character  of  the  silk  fiber  result  from  natural 
causes.  These  alone  are  quite  sufficient  to  necessitate  the 
rigid  examination  of  the  raw  material  in  order  that  its 
subsequent  treatment  may  be  conducted  intelligently. 
The  reader  will  presently  see  that  in  addition  to  these 


6      CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

natural  defects,  which  do  not  permit  of  ready  control  by 
the  silk  grower,  other  defects,  purely  factitious,  are  sub- 
sequently introduced  through  ill-advised  attempts  to  impart 
uniformity  to  the  fiber. 

Viewed  under  the  microscope,  silk  is  seen  to  consist  of 
two  parallel  cylindrical  fibers,  one  of  far  greater  diameter 
than  the  other.  This  duplex  constitution  has  its  origin 
in  the  fact  that  the  thread,  which  is  discharged  in  the  fluid 
state  by  the  worm,  emanates  from  two  distinct  spinarets, 
situated  close  to  the  worm's  under  lip.  These  separate 
threads  unite  after  they  have  emerged  a  short  distance  and 
are  simultaneously  coated  with  the  gum,  which  rapidly 
dries  and  thus  maintains  a  united  and  single  thread. 

Of  the  two  initial  threads  or  "brins"  as  the  French  call 
them,  the  larger  is  the  stronger.  It  is  to  be  noted  that  the 
worm,  when  diseased,  spins  a  thread  in  which  the  smaller 
brin  is  imperfect  and  at  times  absent.  Under  these  cir- 
cumstances the  single  large  brin  is  prone  to  that  splitting 
or  divisibility  which  is  the  true  cause  of  Fiochetti  or  lousi- 
ness. This  subject  is  discussed  more  fully  under  Chapter 
III. 

SERICIN  AND  FIBROIN.  —  The  inner  or  true  silk  fiber  is 
known  technically  as  Fibroin  and  the  gum  coating  as 
Sericin.  Constitutionally  these  are  very  similar,  consisting 
approximately  of 


FIBROIN 

SERICIN 

Carbon 

49  per  cent 

43  per  cent 

Hydrogen  

6  per  cent 

6  per  cent 

Nitrogen  . 

19  per  cent 

16  per  cent 

Oxygen  

25  per  cent 

35  per  cent 

A  comparison  of  these  figures  with  those  given  above  as 
the  approximate  constitution  of  the  dried  worms  and  mul- 


RAW  SILK  7 

berry  leaves  will  prove  an  interesting  substantiation  of 
the  influence  of  diet  upon  the  animal  organism  and  its 
product. 

In  their  chemical,  composition  and  behavior,  Fibroin 
and  Sericin  are  allied  to  gelatin  and  casein.  Hence,  in 
the  subsequent  treatment  of  the  silk  fiber,  these  substances 
may  be  employed  for  "re-animalizing"  the  silk.  Both 
exhibit  characteristic  behavior  towards  certain  chemical 
reagents.  Fibroin,  for  example,  possesses,  per  se,  the  power 
of  reducing  the  higher  chlorides  of  certain  metals  to  the 
lower  chlorides.  It  is  characterized  also  by  the  presence 
of  a  nitro  group  which  permits  of  the  development  of 
certain  shades  within  the  fiber  after  adequate  diazota- 
tion.  Thus,  a  characteristic  color  is  obtained  by  simply 
treating  the  degummed  silk  fiber  with  a  solution  of 
sodium  nitrite  in  hydrochloric  acid,  washing  and  then 
treating  with  a  developer  such  as  phenol,  a  or  )8-naph- 
thol,  resorinol,  etc. 

Both  Fibroin  and  Sericin  are  markedly  hygroscopic, 
i.e.,  they  rapidly  absorb  moisture.  The  normal  moisture 
of  silk  is  estimated  at  11%,  which  figure  is  invariably 
added  to  the  absolute  dry  weight  of  silk  in  order  to  give 
the  conditioned  weight.  Divers  hygroscopic  materials 
have  been  introduced  into  the  fiber  in  the  course  of  reeling 
from  the  cocoon  or  of  throwing,  in  order  to  augment  the 
weighting  of  the  silk  through  the  increased  absorption 
of  atmospheric  moisture,  a  practice  which  is  fortunately 
discouraged  through  conditioning. 

The  solubility  of  Sericin  in  water  is  largely  theoretical, 
although  a  small  proportion  is  soluble  in  this  way.  For 
the  complete  removal  of  the  gum,  however,  advantage 
must  be  taken  of  its  solubility  in  soap  or  alkalies.  The 
latter,  save  borax,  have  an  injurious  effect  on  the  Fibroin. 
Continuous  treatment  with  hot  soda  carbonate  or  caustic 


8      CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

soda,  while  removing  the  Sericin,  also  weakens  the  fiber, 
first  destroying  its  elasticity  and  ultimately  tendering  the 
thread. 

COCOON  REELING.  —  It  is  not  within  the  province  of 
this  work  to  deal  at  length  with  the  commercial  forms  of 
raw  silk,  such  as  tsatlees,  re-reels  or  steam  filatures.  The 
average  silk  manufacturer  is  very  well  informed  as  to  the 
respective  merits  of  these.  To  the  discriminating  weaver, 
cocoon  reeling  offers  an  opportunity  for  study  independent 
of  the  facility  with  which  silk  may  be  thrown  from  the 
several  above-mentioned  forms  of  the  raw  article.  Silk 
manufacture  is  somewhat  similar  to  building  construction, 
although  the  comparison  is  a  trifle  broad.  Once  the 
foundations  are  properly  laid,  the  life  of  the  superstructure 
may  be  predetermined  within  close  limits.  Similarly, 
once  the  quality  of  the  raw  material  is  ascertained,  the 
life  of  the  woven  silk  fabric  may  be  adequately  controlled. 

It  is  in  cocoon  reeling  that  we  see  the  first  evidence  of 
modern  commercial  rapacity.  The  softening  of  the  cocoon 
for  the  purpose  of  facilitating  the  winding  of  the  thread 
is  in  reality  an  extremely  simple  matter;  yet  time  and  skill 
have  been  devoted  to  the  introduction  of  spurious  materials 
in  the  fiber  simultaneous  with  the  softening  of  the  gum, 
that  had  been  more  worthily  directed  to  other  channels. 
A  warm  solution  of  weak  soap  is  all  that  is  required  to 
soften  the  cocoon  preparatory  to  reeling  the  thread.  No 
restriction  applies  to  the  quality  of  the  soap  employed, 
for,  while  a  "good  curd  soap"  has  been  prescribed  as  best 
adapted  to  the  requirement,  opinions  differ  as  to  what 
constitutes  a  good  curd  soap.  With  the  advent  of  cheap 
alkalis,  such  as  sal-soda,  has  come  the  opportunity  to  do 
away  entirely  with  soap  for  the  softening  of  the  cocoons. 
Fatty  oils,  emulsified  into  partial  soaps  through  the  agency 
of  these  alkalis,  have  been  found  cheaper  than  soap  and 


RAW  SILK  9 

yet  as  effective  for  the  purpose.  Were  these  efforts  towards 
economy  confined  to  the  use  of  pure  vegetable  or  animal 
oils,  properly  emulsified,  no  danger  to  the  fiber  could  ensue. 
Such  oils,  however,  may  be  cheapened  still  further  through 
admixture  with  mineral  (petroleum)  oils  which,  once  in- 
troduced into  the  fiber,  are  productive  of  disastrous  re- 
sults because  of  the  various  processes  undergone  by  the 
silk  ere  it  is  in  fit  state  to  be  woven  into  the  ultimate 
fabric. 

Again,  it  is  possible  to  cunningly  incorporate  inert 
mineral  weighting  materials  through  the  agency  of  soften- 
ing media.  The  writer  has  examined  many  Japanese 
silks  with  which  there  has  been  incorporated  a  fine  infu- 
sorial earth,  which  was  detected  only  in  the  course  of  de- 
gumming  in  the  dye-house.  True,  such  adulteration  may 
be  roughly  detected  in  the  boil-off  test  of  the  conditioning 
house,  although  the  character  of  adulteration  can  not  be 
detected  in  this  way.  Apart  from  this,  however,  the  danger 
to  the  thread  through  the  abrasive  action  of  crystalline 
substances  thus  incorporated  is  incalculable.  It  is  pos- 
sible to  admix  a  proportion  of  the  salts  of  alumina  in  the 
course  of  cocoon  softening,  which  admixture  is  revealed 
only  on  analysis.  This  fraud  is  detected  with  difficulty, 
owing  to  the  fact  that  the  ash  of  Bombyx  silk  contains 
normally  about  11%  of  alumina.  An  increase  over  this 
percentage  can  be  legitimately  ascribed  to  the  above 
practice. 

Many  more  practices  could  be  cited  in  support  of  the 
contention  that  he  who  fails  of  systematic  examination  of 
his  raw  silk  must  perforce  proceed  to  the  subsequent 
treatments  on  an  entirely  empirical  basis.  Much  evidence 
exists  in  proof  of  the  fact  that  the  natives  engaged  in  the 
production  of  raw  silk  in  the  Far  East  exercise  at  times 
the  greatest  cunning  in  disposing  of  the  product.  Says 


10    CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

Mr.  Hollins  Rayner,  speaking  as  an  authority  on  this 
subject: 

"To  combat  against  the  well-known  cunning  practised 
in  the  Chinaman's  reeling  and  packing,  the  European  and 
American  shippers  at  Shanghai  and  Canton  are  compelled 
to  have  a  fully  qualified  inspector,  with  assistants,  to 
examine  very  carefully  each  book  of  raw  silk  before  packing 
into  bales  and  shipping.  As  far  as  possible,  without 
damaging  the  silk,  the  books  are  opened  to  see  if  there  has 
been  any  inferior  silk  packed  inside,  which  is  often  the  case. 
Sometimes  the  outside  mosses  are  really  first-class  silk, 
and  look  exceedingly  well,  being  good  color,  bright  and 
fine  in  size;  but  the  inside  layers  have  been  most  cleverly 
made  up  of  coarser,  darker,  and  inferior  silk.  There  have 
been  cases  on  record  where  other  material  besides  silk 
has  been  found  inside  the  books  to  give  weight  to  them, 
but  it  is  only  fair  to  say  that  there  are  some  reliable  Chinese 
dealers  whose  silk  can  generally  be  taken  to  be  what  it 
is  represented  to  be.7' 

If  the  above  is  true  of  conditions  five  or  six  years  ago, 
what  is  to  be  said  of  the  present,  in  the  light  of  the  intro- 
duction of  Western  science  and  the  rapid  spread  of  scien- 
tific information  through  the  Far  East? 

In  simple  justice,  it  is  necessary  to  point  out  that  adul- 
teration of  raw  silk  is  not  confined  to  the  Far  East.  The 
writer  has  examined  numerous  samples  of  Italian  silks 
which  gave  conclusive  evidence  of  tampering  for  the  pur- 
pose of  deception.  He  has  also  examined  samples  of  the 
so-called  European  water  re-reels  which  likewise  fail  to 
show  up  well. 

Although  conditioning  has  done  much  to  abate  these 
evils,  the  very  fact  that  conditioning  methods  cannot  pos- 
sibly determine  with  exactitude  the  nature  of  the  adul- 
terants has  rendered  much  of  the  conditioning  crusade 


RAW  SILK  11 

abortive.  The  writer  repeats  that  is  it  only  through  chem- 
ical analysis  that  any  proper  valuation  of  raw  silk  may 
be  achieved  —  a  valuation  on  which  depends  the  intelli- 
gent application  of  the  processes  through  which  the  silk 
must  go  ere  it  is  woven  into  the  finished  fabric. 


CHAPTER  II 
SILK  THROWING 

THE  preparation  of  a  weavable  thread  from  the  raw  silk 
fiber,  ostensibly  the  simplest  of  all  silk  operations,  is  at 
the  same  time  the  most  important.  While  the  problem 
of  silk  throwing  is  chiefly  mechanical,  involving  the  proper 
twist  of  the  raw  silk  filaments,  the  necessity  of  softening 
the  gum  of  the  raw  ere  it  can  be  wound  prior  to  combining 
the  desired  number  of  filaments  with  the  requisite  twist 
permits  of  a  certain  latitude  in  treating  the  silk,  and  at 
the  same  time  introduces  chemical  considerations  of  thg 
utmost  importance  in  view  of  the  operations  which  the 
thrown  silk  subsequently  undergoes. 

A  great  increase,  during  late  years,  of  the  number  of 
mills  devoted  solely  to  weaving  has  created  a  separate 
industry  —  that  of  throwing  —  of  considerable  magnitude. 
This,  in  turn,  has  created  the  opportunity  for  the  pur- 
chase of  raw  materials  in  the  thrown  state,  ready  for 
dyeing  and  weaving,  of  which  those  manufacturers  who 
regard  the  average  raw  silk  with  suspicion  have  not  been 
slow  to  avail  themselves.  Many,  again,  refuse  to  buy 
thrown  silk,  preferring  to  know  what  chop  they  are  get- 
ting and,  lacking  facilities  for  preparing  organ  and  tram, 
send  the  raw  silk  to  a  commission  throwster.  In  either 
case,  it  follows  that  the  manufacturer  has  absolutely  no 
control  over  his  silk  at  this  most  important  stage.  Where 
silk  is  thrown  " bright, "  i.e.,  where  it  receives  no  soap- 
ing to  assist  the  winding,  any  ensuing  defects  are  purely 
mechanical  in  origin;  but  where,  as  is  commonly  the  case, 

12 


SILK  THROWING  13 

the  silk  is  first  soaked,  chemical  defects  frequently  ensue 
which  do  not  manifest  themselves  until  such  time  as  it  is 
no  longer  possible  to  remedy  them. 

THE  COMMERCIAL  FIBER.  —  Prior  to  winding,  the  silk 
is  split  into  slips  of  convenient  size,  as  too  much  material 
on  the  swifts  causes  the  thread  to  break  constantly,  re- 
sulting in  an  excess  of  knotted  ends  in  the  skein.  The  raw 
silk  fiber  is  also  frequently  cleaned,  mechanically,  by  wind- 
ing from  one  bobbin  to  another,  the  thread  meanwhile 
passing  through  a  guide  or  cleaner. 

The  commercial  silk  fiber  is  of  three  kinds :  Organzine,  for 
warp,  Tram  for  weft  or%filler,  and  "  No-throw. "  Occasion- 
ally, for  special  goods,  "  Singles, "  consisting  of  iJie  thread  as 
delivered  by  the  cocoon  reeler  or  just  sufficienl^twisted  to 
resist  the  operations  of  stripping  and  dyeing,  is  employed. 

The  chief  factor  in  the  preparation  of  commercial  silk 
yarn  is  the  twist  given  to  the  thread,  and  in  this  respect 
organzine  and  tram  differ  only  in  so  far  that,  in  the  case  of 
organ,  the  individual  thread  is  given  twist  as  well  as  the 
combined  threads;  whereas,  in  tram,  the  single  fiber  re- 
ceives no  twist  whatever,  the  twist  being  imparted  solely 
to  the  combined  threads.  Both  organ  and  tram  may  con- 
sist of  two  or  more  threads,  although  two-thread  organ  is 
the  average  while  three  threads  constitute  the  minimum 
combined  in  tram.  "No-throw"  is  a  thread  without 
twist;  just  doubled,  or  at  the  most  given  just  enough  twist 
to  combine  the  fibers.  The  a/nount  of  twist  is  controlled 
by  the  manufacturer's  individual  requirement.  Organzine 
is  always  a  much  tighter  and  finer  thread  than  tram  and 
for  this  reason  is  never  weighted  so  heavily  as  tram.  The 
latter,  being  more  open  than  organ,  is  usually  brighter 
after  weighting  and  dyeing.  It  takes  up  weight  far  more 
readily  than  organ,  because  of  this  very  openness  of  the 
thread. 


14    CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

THROWING  MATERIALS  AND  PROCESS.  —  By  far  the 
greater  part  of  thrown  silk  is  softened  or  soaked  before 
winding  —  an  operation  in  no  wise  complicated.  In 
American  practice  the  silk  is  soaked  over  night  in  a  bath 
containing  soap  (made  from  olive  oil  foots),  neatsfoot 
oil  and  a  little  borax.  A  few  prefer  to  use  a  good  grade 
of  olive  oil  in  place  of  the  neatsfoot,  although  it  is  generally 
conceded  that  pure  neatsfoot  oil  is  better  for  the  silk.  The 
quantity  of  the  above  materials  to  be  employed  is  subject 
to  the  hardness  of  the  silk  gum.  This  is  softest  in  Japan 
stock,  intermediate  in  Canton  and  Italian,  and  hardest  in 
Bengal.  The  average  formula  for  soaking  50  Ibs.  of  Japan 


in  60  gallons  water 


3  Ibs. 

Neatsfoot  Oil  ....  3  quarts 
Borax. .  .  2  oz. 


To  soften  50  Ibs.  of  Bengal,  double  this  quantity  of  materials 
would  be  required. 

CLEARANCE.  —  Curiously  enough,  the  majority  of  prac- 
tices publicly  condemned  by  silk  manufacturers  are  se- 
cretly condoned  by  them  and  inevitably  traceable  to  their 
own  cupidity.  No  exception  to  this  rule  is  the  secural 
of  clearance  on  thrown  silks.  Since  the  softening  of  the 
silk  gum  by  means  of  the  oil,  soap,  and  borax  involves  a 
slight  loss  of  weight  through  the  stripping  action  of  the 
bath,  the  throwster  is  authorized  to  return  an  excess  of 
the  weight  of  the  raw  silk  received  by  him,  up  to  5%. 
Thus  if  1000  Ibs.  of  silk  are  thrown,  1050  Ibs.  may  be  re- 
turned, to  which  extra  50  Ibs.  no  cost  attaches  for  the 
throwster's  services.  We  have,  in  this  practice,  the  very 
root  of  the  present  evils  of  silk  manufacture.  It  is  an 
ingenious  system  of  " robbing  Peter  to  pay  Paul,"  that,  so 
far  from  advantaging  any  one,  creates  considerable  trouble. 
Normally,  this  clearance  consists  of  so  much  extra  soap 


SILK  THROWING  15 

and  oil  absorbed  by  the  silk  as  it  soaks,  which  added 
weight  promptly  comes  off  in  the  dyer's  stripping  box. 
Frequently,  it  is  obtained  through  the  introduction  of 
materials  which  do  not  readily  strip  off,  or  of  partially 
soluble  materials  which  contaminate  the  dyer's  baths. 

Some  manufacturers  so  far  delude  themselves  as  to 
believe  that  the  throwster's  clearance  gives  them  an  ad- 
vantage over  the  dyer  in  that  part  of  the  weight  of  the 
thrown  silk  submitted  to  the  latter  is  factitious  and  must 
be  replaced  in  weighting  at  the  dyer's  expense.  Such  in 
reality  deceive  only  themselves,  as  the  following  will 
doubtless  serve  to  illustrate. 

The  manufacturer  purchases,  let  us  assume,  1000  Ibs. 
of  raw  silk,  at  a  cost  roughly  of  $5000.  Since. some  silk 
boils  off  as  low  as  18%  and  some  as  high  as  30%,  the  dyer, 
throughout  his  operations,  assumes  an  average  25%  as  the 
boil-off  of  all  silk.  Taking  this  figure,  the  1000  Ibs.  of 
raw  silk  represents  750  Ibs.  of  ultimate  silk  fiber  at  a  cost 
of  $5000.  The  silk  is  thrown  and  1050  Ibs.  are  returned, 
the  additional  50  Ibs.  consisting,  we  shall  assume,  of  pure 
soap  and  oil.  All  that  has  happened  thus  far  is  the  increase 
of  the  boil  off  loss  of  this  silk  from  25%  to  28J%.  The 
manufacturer  has  thus  far  gained  not  a  single  ounce  of 
ultimate  fiber.  Let  the  weight  ordered  be  24  oz. 

Had,  now,  1000  Ibs.  of  thrown  silk  been  sent  to  the  dyer, 
in  the  customary  number  of  passes,  he  would  have  obtained 
24  oz.  full  and  returned  1500  Ibs.  of  weighted  silk,  of  which 
750  Ibs.  would  still  represent  the  ultimate  fiber.  As  it 
is,  the  dyer  receives  1050  Ibs.  of  material  and,  with  the 
customary  number  of  passes,  obtains  only  a  little  more 
than  22  oz.  weight.  Since  the  dyer  receives  exactly  the 
same  price  whether  he  puts  in  the  22  oz.  or  the  24  oz.,  it 
is  difficult  to  comprehend  where  the  manufacturer  gains 
by  the  operation.  As  a  matter  of  fact,  he  is  the  loser 


16    CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

because  of  this  clearance.  Had  the  normal  boil-off  of  his 
silk  been  undisturbed,  the  manufacturer  would  have  been 
the  gainer  by  over  an  ounce  to  the  pound,  whereas,  with 
the  1050  Ibs.,  if  he  insist  on  full  24  oz.,  he  gets  back  just 
so  much  more  tin  silico-phosphate,  owing  to  the  fact  that 
the  dyer  must  work  the  silk  more  to  get  the  weight. 

If,  on  the  other  hand,  the  silk  is  to  be  dyed  pure,  the 
manufacturer  neither  gains  nor  loses  through  the  throw- 
ster's clearance.  The  dyer  certainly  does  not  lose  in  any 
event.  If  his  profit  is  slightly  decreased  because  of  the 
necessity  of  further  treatment  on  his  part,  the  manufac- 
turer is  a  greater  loser  because  of  the  added  weighting 
materials  in  his  silk.  Thus,  where  1000  Ibs.  are  submitted 
and  1500  Ibs.  returned,  one-half  of  the  weighted  silk  is 
true  fiber;  but  where  1050  Ibs.  were  submitted,  the  50  Ibs. 
being  the  throwster's  clearance,  and  the  dyer  obtains  full 
24  oz.,  he  returns  1575  Ibs.,  of  which  750  Ibs.,  now  kss  than 
half  of  the  material,  still  represents  the  true  silk  fiber. 
What  has  the  manufacturer  gained?  In  the  first  instance, 
for  a  given  price  the  dyer  returns  50%  silk,  50%  weighting. 
In  the  second,  for  the  same  price,  the  dyer  returns  47.6% 
true  silk  and  52.4%  weighting.  The  manufacturer  has 
thus  lost  2J%  of  silk  fiber.  The  extra  75  Ibs.  returned 
by  the  dyer  is  all  weight  and  he  is  paid  for  this  at  the  same 
rate  as  if  it  were  half  fiber  and  half  weight.  What  has  the 
dyer  lost?  Nothing.  What  has  the  manufacturer  gained? 
An  over  loaded  fiber. 

We  are  not  so  much  concerned  in  these  pages  with 
the  commercial  fallacy  of  clearance,  but  rather  with  the 
chemical  aspects  of  the  practice — although  the  latter  have 
considerable  bearing  on  the  former. 

INFLUENCE  OF  THROWING  ON  SUBSEQUENT  OPERATIONS. 

-It  is  in  the  materials  employed  in  throwing  that  we 

encounter  the  first  element  of  danger  to  the  ultimate 


SILK  THROWING  17 

woven  fabric.  Were  the  soap  and  neatsfoot  oil  always 
pure,  and  did  the  throwster  always  content  himself  with 
clearance  resulting  from  the  natural  absorption  of  these 
by  the  silk,  one  could  scarcely  look  to  throwing  as  the 
cause  of  many  of  the  defects  in  finished  silk.  These 
ingredients,  however,  are  not  as  a  rule  pure  and  are  fre- 
quently badly  contaminated. 

True  neatsfoot  oil  is  obtained  from  the  hoofs  of  cattle. 
Of  the  neatsfoot  oils  on  the  market,  only  the  highest  priced 
are  obtained  from  this  source  through  careful  processes  of 
rendering.  The  true  oil  is  characterized  by  the  absence 
of  the  higher  fatty  acids,  such  as  stearates,  exhibiting,  in 
consequence,  a  very  low  freezing  point  or  cold-test.  Thus, 
a  good  neatsfoot  oil  will  not  congeal  above  12°  F.  or  20° 
lower  than  the  freezing  point  of  water.  Some  have  as 
low  a  cold  test  as  4°  F.  Such  oils  are,  in  addition,  char- 
acterized by  the  absence  of  free  fatty  acids  beyond  a  mere 
trace.  Among  the  neatsfoot  oils  coming  into  the  market 
are  those  rendered  from  low  greases  and  animal  stock, 
by  treatment  with  mineral  acids  and  other  means.  Such, 
although  classified  as  neatsfoot,  are  in  no  sense  neatsfoot. 
These  oils  have  a  very  high  cold-test,  usually  congealing. 
at  32°  F.  and  some  higher.  Left  to  stand  at  ordinary 
room  temperature,  quantities  of  stearates  separate  out. 
In  addition,  they  are  rich  in  free  fatty  acids  the  action  of 
which  is  described  below. 

The  soap  employed  by  the  throwster  is  usually  beyond 
criticism.  It  is  the  same  as  the  dyer  uses  in  stripping  and, 
though  occasionally  containing  unsaponified  fats,  it  is 
ninety-nine  times  out  of  a  hundred  normal. 

The  high  cost  of  pure  neatsfoot  oil  does  not  tempt  the 
average  throwster  to  purchase  and  use  it,  and  because  of 
his  efforts  toward  economy,  without  his  always  being  aware 
of  it,  he  almost  constantly  endangers  the  silk  entrusted 


18    CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

to  him.  To  secure  an  oil  for  throwing  at  60/  per  gallon 
means  one  of  two  things.  He  gets  either  true  neatsfoot 
mixed  down  with  white  petroleum  oil,  or  one  of  the  so- 
called  neatsfoot  oils,  rich  in  stearates  and  free  acids.  Even 
these  are  at  times  adulterated  with  petroleum  oil.  Few, 
if  any,  throwsters  go  to  the  trouble  of  having  their  oils 
examined  for  their  purity. 

The  borax  used  to  emulsify  the  soap  and  oil  is  usually 
standard,  although  it  has  been  adulterated  at  times  with 
common  salt  and  even  caustic  soda,  which  latter  has  a 
drastic  weakening  action  on  the  thread. 

Taken  all  in  all,  uncontrolled  throwing  is  a  serious 
menace  to  the  quality  of  the  ultimate  fabric.  If  the  throw- 
ster's oil  contains  stearates  and  free  fatty  acids,  these  per- 
meate the  fiber  and  are  with  difficulty  removed  in  stripping. 
Indeed,  unless  the  dyer  is  aware  of  their  presence  they 
practically  defy  removal,  requiring  as  they  do  an  excess 
of  soda  in  the  stripping  bath,  which  weakens  the  thread 
in  order  to  saponify  them  and  render  them  water-soluble. 
Unless  they  are  removed,  they  combine  with  the  ingredi- 
ents of  the  weighting  bath,  forming  insoluble  soaps,  which 
refuse  to  dye  evenly,  frequently  remaining  sticky  and  hin- 
dering the  winding  of  the  dyed  silk  and  even,  at  times, 
causing  chalkiness  of  the  dyed  silk. 

Even  more  serious  than  this  is  the  menace  of  petroleum 
oil  once  introduced  into  the  silk  fiber.  The  exact  action 
of  this  is  fully  described  in  Chapters  III,  V  and  VI.  The 
following  is  a  case  in  point. 

As  is  well  known,  souple  silk  is  prepared  by  simply 
softening  the  gum  and  not  stripping  it  off.  This  was  for- 
merly done  by  means  of  tar  tar  ic  acid.  More  recently, 
the  silk  is  subjected  to  a  bath  of  mixed  sulphuric  and 
sulphurous  acids  until  the  gum  has  swollen  to  the  requi- 
site degree,  when  the  " honeycombing"  is  filled  by  means 


SILK  THROWING  19 

of  cane  sugar,  or  better  and  cheaper  still,  glucose.  After 
weighting  and  dyeing,  the  stiffness  is  removed  on  a  break- 
ing machine. 

In  June  of  this  year,  the  writer  was  called  upon  to 
determine  the  cause  of  black  streaks,  greasy  in  nature, 
in  some  heavily  weighted  taffeta  for  petticoats.  The  facts 
in  the  case  were  these.  The  silk,  several  thousand  pounds, 
had  been  dyed  by  a  prominent  commission  dyer  in  Febru- 
ary, 1908.  Part  of  the  tram  was  dyed  bright  i.e.,  the  gum 
boiled  off,  and  part  was  dyed  souple.  All  was  weighted 
24  oz.  full.  The  silk  was  returned  to  the  manufacturer 
who  wove  it  on  a  rush  order,  which  order  was  counter- 
manded when  the  silk  was  ready  for  delivery.  The  silk 
was  accordingly  stored  away  hi  the  vaults.  Seventeen 
months  later  it  was  taken  out  preparatory  to  delivery  on 
another  order,  and  when  examined  so  much  as  was  woven 
from  the  soupled  tram  was  found  to  be  full  of  black  streaks 
running  through  the  goods  in  the  direction  of  the  filler. 
Goods  that  had  been  woven  with  bright  tram  were  fault- 
less. It  is  to  be  noted  that  the  goods,  immediately  they 
were  woven,  seventeen  months  previous,  had  been  examined 
and  pronounced  perfect. 

Of  course,  the  inevitable  claim  was  lodged  against  the 
dyer,  who  contended  that  the  fault  was  not  his.  The  spots 
were  proven  to  be  grease  of  some  kind  and  for  a  while  it 
was  thought  that  they  were  the  result  of  the  casein  com- 
bined with  the  phosphate  bath.  In  fact,  superfatted 
casein  applied  to  the  silk  produced  spots  or  streaks  iden- 
tical with  those  complained  of.  It  is  to  be  noted,  however, 
that  the  bright  tram  in  the  other  goods,  although  it  had 
received  the  casein  treatment  at  the  same  time  as  the  souple, 
exhibited  none  of  the  defects  of  the  latter. 

Experience  with  similar  complaints  led  the  writer  to 
direct  his  investigation  elsewhere,  with  the  result  that  the 


20    CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

streaks  were  found  to  consist  essentially  of  petroleum  or 
mineral  oil.  This  view  was  subsequently  confirmed  by 
the  laboratory  at  Milan,  Italy,  to  whom  the  matter  was 
ultimately  referred  for  a  final  opinion.  It  is  not  at  all 
difficult  to  trace  the  action  of  the  mineral  oil,  introduced 
by  the  throwster  in  this  case.  In  the  case  of  the  bright 
tram,  the  bulk  was  removed  in  the  stripping.  In  that 
which  was  soupled,  however,  the  combination  of  neatsfoot 
and  mineral  oils,  employed  by  the  throwster,  was  prac- 
tically permanently  fixed  in  the  fiber  by  the  combined 
acids  of  the  soupling  bath.  Subsequently  weighted  with 
tin,  the  latter  formed  partial  tin  soaps  within  the  fiber. 
For  the  dissociation  of  these  both  time  and  heat  are  re- 
quired. These  factors  were  secured  by  storing  the  silk 
when,  as  is  well  known,  considerable  heat  develops  in 
weighted  silk  —  so  much  so  that  insurance  companies 
refuse  heavily  weighted  silks  as  a  risk.  The  storing  of  the 
silk,  then,  supplied  all  that  was  necessary  for  the  gradual 
dissociation  of  the  metallic  soaps  within  the  fiber  and  the 
ultimate  sweating  out  of  the  grease,  which  was  heaviest 
wherever  the  silk  was  folded,  i.e.,  where  the  greatest 
heat  was  generated.  Need  anything  more  be  said  to 
convince  the  manufacturer  of  the  necessity  of  determining 
what  is  in  the  thrown  silk  before  sending  it  to  the  dyer? 
To  return  to  the  subject  of  clearance.  No  possible  good 
from  this  accrues  to  the  manufacturer  where  this  consists 
of  an  excess  of  pure  soap  and  oil. '  Where  these  are  impure 
manifest  harm  results  —  so  much  more  dangerous  impuri- 
ties introduced  into  the  silk,  than  is  necessary.  Where,  to 
stimulate  the  absorption  by  the  silk  of  the  oil  emulsion, 
the  throwster  employs  salt,  the  menace  is  increased.  It  is 
useless  to  occupy  the  reader's  time  with  a  discussion  of 
the  possibility  of  introducing  insoluble  materials  in  the 
silk,  thus  obtaining  a  clearance  which  is  permanent.  Such 


SILK  THROWING  21 

practices  are  fortunately  rare  and  are  readily  detected. 
The  menance  of  the  use  of  adulterated  materials  by  the 
throwster  is  sufficiently  great  without  stopping  to  inquire 
if  he  resorts  to  downright  trickery,  which  is  extremely 
doubtful. 

Those  weavers  who  do  their  own  throwing  and  dyeing, 
although  in  far  better  case  than  those  who  have  to  resort 
to  the  commission  throwster,  inasmuch  as  clearance  is 
not  an  item  with  them,  are  still  not  immune  to  the  danger 
of  adulterated  throwing  materials.1  Yet  they  are  in  some- 
what better  position  to  check  these  even  though  roughly, 
inasmuch  as  many  untoward  conditions  in  the  dye-house 
can  be  traced  back  to  the  throwing  department  as  fast  as 
they  arise.  On  the  other  hand,  the  manufacturer  who  is 
dependent  upon  both  commission  throwster  and  commis- 
sion dyer  for  the  treatment  of  his  silk  at  stages  of  the 
utmost  importance,  frequently  courts  disaster  and  is  at 
best  the  recipient  of  mediocre  results  through  his  failure 
to  inform  himself  of  the  constitution  of  the  raw  silk  before 
it  goes  to  the  throwster,  and  that  of  the  thrown  silk  before 
he  sends  it  to  the  dyer. 

1  See  case  described  in  Chapter  III,  page  29. 


CHAPTER  III 
SILK   STRIPPING 

SILK  stripping  or  degumming  is  the  first  of  a  series  of 
operations  for  the  success  or  failure  of  which  the  dyer  is, 
under  normal  conditions,  responsible.  Assuming  that  the 
silk  which  comes  to  him  to  be  dyed  has  not  suffered  the 
various  questionable  practices  in  cocoon  reeling  or  throw- 
ing that  have  been  described  in  the  foregoing  pages,  it 
rests  with  the  dyer  whether  the  silk  shall  leave  his  works 
in  good  condition  or  not.  In  view  of  the  extent  of  these 
questionable  practices  at  the  present  time,  it  is  doubtful 
if  the  dyer  is  responsible  for  the  majority  of  the  defects 
commonly  complained  of  in  the  finished  silk. 

HARDNESS  OF  SERICIN.  —  Gum  hardness  varies  with 
the  different  kinds  of  silk.  Japan  has  about  the  softest 
gum  of  all;  Bengal  the  hardest.  Intermediate  are  Can- 
ton, China,  and  the  Italian  silks  —  yellow  and  green. 
The  relative  hardness  of  the  gum  naturally  receives  con- 
sideration in  the  boil-off,  controlling  the  temperature  at 
which  the  operation  is  conducted  as  well  as  its  duration. 

STEAM  STRETCHING.  —  Prior  to  boiling  off  the  silk,  it 
may,  where  extra  brilliance  or  luster  is  desired,  be  stretched 
in  the  gum.  Opinion  differs  as  regards  the  advisability 
of  this  practice.  In  our  larger  dye-houses  it  has  been 
superseded  by  the  so-called  metallicing  machines  the 
operation  of  which  is  fully  described  in  Chapter  VI. 

It  is  contended  that  gum  stretching  tends  to  weaken 
the  silk,  lessening  its  elasticity.  The  writer  grants  that 
such  danger  exists  where  the  process  is  carelessly  carried 

22 


SILK  STRIPPING  23 

out.  Taken  all-in-all,  however,  it  is  the  safest  of  all  the 
processes  designed  to  produce  extra  brilliance.  In^the 
first  place  it  is  effected  at  a  stage  where  the  silk  ha™een 
only  lightly  treated  —  where,  under  normal  conditions,  no 
extraneous  materials  other  than  pure  oil,  pure  soap,  and 
a  trifle  of  borax  have  entered  the  fiber;  whereas,  in  the 
case  of  metallicing  after  dyeing,  the  silk  has  undergone 
numerous  complex  operations.  Secondly,  the  luster  pro- 
duced by  gum  stretching  is  permanent  so  long  as  succeed- 
ing operations  are  correctly  executed,  while  the  luster  of 
metallicing  does  not  always  endure. 

Prior  to  gum  stretching,  the  thrown  silk  is  softened 
over  night  in  a  lukewarm  bath  containing  10%  of  the 
weight  of  the  silk  in  soap  and  just  enough  water  to  cover 
the  silk.  The  following  morning  the  excess  of  soap-water 
is  removed  by  whizzing  in  the  hydro-extractor  and  the 
silk  must  then  be  stretched  at  once. 

The  stretching  apparatus  varies  in  construction.  The 
simplest,  which  happens  to  be  tlie  best,  consists  of  a  small 
chamber  containing  two  metal  pins,  the  upper  permanent, 
the  lower  movable  at  will.  Over  these  a  limited  number 
of  skeins  i&  put.  The  chamber  is  then  closed  and,  simul- 
taneous with  a  blast  of  high-pressure  steam,  the  under 
pin  is  lowered  the  desired  distance,  allowed  to  rest  for 
an  instant  and  the  tension  released,  at  the  same  time 
cutting  off  the  steam.  The  batch  is  then  removed  and  a 
fresh  batch  entered.  The  simultaneous  stretching  and 
steaming  presupposes  considerable  skill  on  the  part  of  the 
operator.  The  steam  must  be  free  from  moisture,  else 
the  silk  is  degummed  in  spots  which  are  over-stripped  in 
the  subsequent  degumming  bath.  (See  Fiochetti  below.) 

MATERIALS  EMPLOYED.  —  The  chief  of  these  is,  of  course, 
soap;  and  the  soap  employed  is  usually  that  made  from 
olive  oil  foots  (the  so-called  sulphur  oil).  The  constitu- 


24    CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

tion  of  this  soap  is  important.  If  the  soap  be  too  neutral 
or  ^diibit  free  unsaponified  fats,  its  stripping  action  is 
retried  and  the  treated  silk  apt  to  be  greasy.  (See  same 
problem  in  throwing.)  If,  on  the  other  hand,  the  soap 
contains  a  marked  excess  of  free  caustic  alkali,  it  is  apt 
to  tender  the  thread.  A  soap  that  is  on  the  alkaline  side, 
but  showing  not  more  than  one-half  of  one  per-cent  free 
caustic  alkali,  is  best  for  stripping. 

To  insure  the  alkalinity  of  the  stripping  bath,  or,  where 
hard  water  alone  is  available,  it  has  been  customary  to 
employ  carbonate  of  soda  (sal  soda  or  soda  ash)  in  addition 
to  the  soap.  This  practice  is  somewhat  risky,  as  solu- 
tions of  soda  at  the  temperature  obtaining  in  this  process 
have  a  decided  weakening  tendency  on  the  thread.  Borax 
might  be  employed  with  greater  safety,  but  its  cost  is 
practically  prohibitive. 

When  these  alkalies  are  employed,  or  where  too  alkaline 
a  soap  is  used,  not  only  does  the  silk  suffer  this  weakening 
action,  but  the  sodium  salts  remaining  in  the  fiber  because 
of  inadequate  washing  are  apt  to  cause  considerable 
mischief  in  the  "dynamite"  bath.  The  best  stripping 
practice  presupposes  the  use  of  only  soap  which  is  just 
alkaline  enough  hi  constitution,  and  of  this  there  is  used 
from  25  to  30%  based  on  the  weight  of  the  silk  worked. 

THE  STRIPPING  PROCESS.  —  The  silk  is  placed  on  the 
sticks  and  is  worked  in  the  bath,  being  given  the  requisite 
number  of  turns  (three  in  all),  until  all  the  gum  is  off. 
Apparently  a  matter  of  extreme  simplicity,  in  reality 
considerable  skill  is  involved  in  silk  stripping.  The  selec- 
tion of  a  box  that  is  neither  too  large  nor  too  small  to 
accommodate  the  lot,  and  yet  permits  of  free  movement 
of  the  skeins,  involves  some  judgment.  The  skeins  are 
moved  very  slowly,  as  quick  action  tends  to  "fuzz"  the 
goods. 


SILK  STRIPPING  25 

Assuming  that  one  hundred  pounds  are  being  worked 
the  stripping  consumes  two  hours.  After  the  gum  has 
been  dissolved,  the  silk  is  washed  several  times  and  Anally 
receives  a  bath  of  acetic  acid. 

In  stripping,  mill  dye-house  practice  naturally  differs 
from  that  obtaining  in  commission  dye-houses.  In  the 
former,  it  is  possible  to  separate  the  boiled-off  liquor  from 
colored  gum  silks  from  that  which  results  from  stripping 
white  gum  silk.  This  is  not  always  expedient  in  commis- 
sion dye-houses.  Here,  because  of  the  great  amount  of 
work  to  be  done  in  a  given  time,  and  the  necessity  for 
economizing  in  materials  consumed,  as  well  as  labor,  it 
is  frequently  necessary  to  first  strip  white  silk,  then  re- 
strengthen  the  bath  and  at  once  strip  yellow  silk.  In  this 
way  the  liquors  are  mixed. 

It  is  commonly  known  that  the  bath,  containing  the 
gum  from  the  stripped  silk,  constitutes  the  basis  of  the 
dye-bath  after  adequate  dilution  with  water.  (See  Chapter 
VI.)  Where  the  various  colored  liquors  may  be  kept 
separate,  the  dyeing  of  light  shades  is  simplified,  as  none 
but  the  boil-off  liquor  from  white  gum  silks  is  used  for 
this  purpose,  that  from  the  yellow  being  employed  for 
the  dark  shades.  Where  the  liquors  are  mixed,  at  the 
outset  of  stripping,  as  is  the  case  in  some  commission  dye- 
houses,  it  is  not  possible  to  obtain  the  same  clearness  of 
light  shades  as  can  be  obtained  if  the  liquors  are  kept 
separate  as  described. 

Again,  in  some  of  the  small  commission  dye-houses,  the 
simultaneous  stripping  of  Japan,  yellow  Italian,  and  Can- 
ton is  frequently  attempted.  The  fallacy  of  this  practice 
becomes  manifest  upon  study  of  the  influence  of  tempera- 
ture on  stripping.  When  these  three  are  worked  in  the 
same  bath,  if  the  Italian  is  stripped,  the  Japan  and  Can- 
ton are  bound  to  be  over-stripped.  If  the  Japan  is  prop- 


26    CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

erly  degummed,  the  Canton  will  be  too  much  so  and  the 
Italian  only  partially  so.  When  the  Canton  is  stripped, 
neither  the  Japan  nor  the  Italian  will  be  fully  stripped. 
Again,  the  yellow  gum  of  the  Italian  is  apt  to  stain  the 
other  two,  with  the  result  that,  if  they  are  to  be  dyed 
white,  an  excess  of  blue  is  required,  imparting  a  bluish 
cast;  and  they  will  not  be  clear  if  dyed  into  intermediate 
light  shades.  For  the  darker  shades  this  practice  does 
not  interfere  to  any  extent. 

INFLUENCE  OF  TEMPERATURE.  — According  as  the  hard- 
ness of  the  silk  gum  varies,  so  is  the  temperature  at  which 
the  stripping  bath  is  maintained  regulated,  as  well  as 
the  time  between  " turns.''  Thus  in  stripping  Japan 
stock,  the  bath,  once  brought  to  the  boiling  point,  is 
permitted  to  cool  gradually  after  the  silk  has  been 
entered,  and  only  twenty  to  twenty-five  minutes  are 
given  between  turns.  On  the  other  hand,  for  yellow 
Italian  silk  (particularly  organzine  which  has  a  tight 
twist),  the  bath  is  maintained  at  as  near  the  boiling 
point,  throughout  the  entire  operation,  as  is  possible 
without  creating  actual  ebullition.  Again,  when  Canton 
is  stripped,  the  temperature  should  not  exceed  180°  F., 
as  greater  heat  promotes  this  silk's  exasperating  ten- 
dency to  "fuzz." 

INFLUENCE  OF  WATER.  —  The  character  of  the  water 
employed  is  most  important.  This  should  be  very  soft, 
else  there  are  at  once  introduced  into  the  silk,  in  stripping, 
very  harmful  substances  that  emanate  from  the  same  source 
as  in  throwing. 

Unless  the  water  be  soft,  the  silk  will  not  emerge  from 
the  strip  with  adequate  luster;  and  the  luster  cannot  be 
restored  in  subsequent  processes  without  radical  danger 
to  the  thread. 

SOUPLE.  —  The  preparation  of  souple  has  already  been 


SILK  STRIPPING  27 

described  in  connection  with  the  use  of  mineral  oils  in 
throwing.  (See  p.  18.) 

STRIPPING  TUSSAH.  —  Tussah  should  never  be  stripped 
on  soap,  as  this  tends  to  permanently  bind  the  coloring 
matter  in  the  fiber  and  renders  bleaching  extremely  diffi- 
cult if  not  actually  impossible.  Accordingly,  Tussah  is 
stripped  in  a  bath  containing  25%  of  its  weight  of  silicate 
of  soda.  The  temperature  and  modus  operandi  are  the 
same  as  in  regular  stripping  save  that  more  acid  is  required 
to  rid  the  fiber  of  all  traces  of  silicate. 

FIOCHETTI  OR  " LOUSINESS."  -The  phenomenon,  only 
recently  explained,1  of  the  appearance  of  white  specks 
on  the  thread  of  dyed  silks,  which  specks  interfere  with 
weaving,  long  constituted  a  puzzle  to  dyer  and  weaver 
alike.  It  was  long  known  that  diseased  worms  spun  a 
fiber  which,  when  dyed,  exhibited  this  defect,  commonly 
termed  "lousiness";  but  because  of  the  paucity  of 
information  on  the  subject,  this  defect  was  invariably 
ascribed  to  " lousiness"  where  recent  research  has  proven 
conclusively  that  a  similar  phenomenon,  and  one  readily 
mistaken  for  the  original,  has  its  origin  in  the  initial  treat- 
ment of  the  silk  fiber,  and  that  ninety-nine  out  of  a  hun- 
dred cases  of  so-called  lousiness  are  due  to  factors  other 
than  disease  of  the  worm. 

After  years  of  patient  and  exhaustive  research,  the  late 
Sir  Thomas  Wardle,  long  time  president  of  the  Silk  Asso- 
ciation of  Great  Britain,  his  observations  subsequently 
confirmed  by  the  researches  of  the  Societa  Cooperativa  del 
Sete,  of  Milan,  demonstrated  that  conditions  at  intervals 
obtain  beyond  the  control  of  sericulturists  which  induce 
the  worm  to  spin  a  thread  characterized  by  its  divisi- 
bility once  the  gum  is  removed.  Such  a  thread  splits 

1  For  a  description  of  the  cause  of  true  lousiness,  see  "  Divisibility  of 
the  Silk  Fiber,"  Sir  Thomas  Wardle,  Leek. 


28    CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

into  tendrils,  or  fine  fibers,  viewed  clearly  only  with  the 
microscope,  which  tend  to  bunch  together  on  the  main 
fiber.  To  the  naked  eye  these  become  visible  only  after 
the  silk  is  dyed. 

Owing  to  the  fact  that  the  form  and  constitution  of 
these  fibrillse  is  changed  because  of  disease  in  the  worm, 
with  the  result  that,  under 'the  lens  of  the  microscope,  they 
appear  flat  and  segmented  like  cotton,  an  ingenious  theory 
as  to  their  origin  was  promulgated  some  years  ago.  It 
was  claimed  that  fine  fibrils  of  wood  (cellulose)  were  de- 
tached from  the  stripping  box  by  the  constant  action  of  the 
hot  soap  (this  despite  the  fact  that  stripping  boxes,  as 
well  as  others  of  wood  employed  in  the  dye-house,  are  all 
canvas  lined),  and,  attaching  themselves  to  convenient 
places  in  the  silk,  became  more  firmly  lodged  in  the  course 
of  treating  the  silk,  ultimately  forming  these  minute 
fibrillae. 

The  absurdity  of  this  contention  becomes  at  once  mani- 
fest if  we  pause  to  reflect  that,  even  were  it  possible  for 
minute  slivers  of  the  wood  to  attach  themselves  to  the 
silk,  they  would  be  dyed  more  or  less  the  same  shade  as 
the  silk  and  hence  pass  detection;  or,  if  observed  at  all, 
they  would  be  regarded  as  fuzz  caused  by  over-stripping 
or  some  such  error  in  manipulating  the  silk.  It  is  well 
known,  however,  that  the  minute  "nests"  of  fibrillaB  which 
are  true  fiochetti  or  "lousiness"  are  incapable  of  absorb- 
ing any  dye-stuff  and  hence  appear  as  pure  white  specks 
upon  the  dyed  fiber.  The  writer  does  not  contend  that 
specks  of  this  character  do  not  frequently  appear  on  dyed 
silks.  He  asserts,  however,  that,  in  the  majority  of  cases, 
the  origin  of  these  specks  is  traceable  to  factors  other 
than  disease  in  the  worm. 

A  defect  very  similar  in  appearance  to  fiochetti  may 
result  from  the  following: 


SILK  STRIPPING  29 

1.  Faulty  practice  in  gum  stretching.     Unless  the  silk 
is  stripped  immediately  after  it  is  stretched  in  the  gum, 
the  latter  will  harden  in  spots,  causing  these  to  over-strip 
by  the  time  of  their  complete  removal  in  the  soap  bath, 
Again,  if  the  silk  is  stretched  too  much  in  the  gum,  the 
latter  becomes  firmly  embedded  in  the  fiber  in  spots,  with 
the  same  result. 

2.  Over-stripping.     The  too  rapid  movement  of  the  silk 
in  the  soap  bath  or  its  retention  for  too  long  a  time  in  the 
bath.     The  permitting  of  actual  ebullition  of  the  bath 
while  the  silk  is  immersed  therein. 

3.  The  use  of  very  hard  water  for  stripping.     The  lime 
and  magnesia  (and  at  times,  iron),  in  hard  water  unite 
to  form  lime,  magnesia,  or  iron  soaps  as  the  case  may  be, 
with  the  soap  of  the  bath.    These  insoluble  metallic  soaps 
form  within  the  fiber  and  are  rarely  if  ever  split  up.     They 
do  not  dye  readily  and  hence,  wherever  formed,  have  the 
specky  appearance  of  lousiness. 

4.  The  use  of  petroleum  oil  in  throwing.     This  is  by 
far  the  commonest  cause  of  speckiness  of  the  dyed  fiber, 
producing  a  result  so  akin  to  true  lousiness  as  to  puzzle 
experts.     That  this  may  be  caused  by  the  above  oil  is, 
however,  indisputable. 

Four  years  ago  the  writer  was  called  upon  to  determine 
the  cause  of  speckiness  of  some  silk  dyed  pink  and  light 
blue.  In  addition  to  exhibiting  specks,  a  fuzzy  coating 
was  scraped  off  as  the  silk  passed  through  the  loom,  clog- 
ging the  reed-harness  and  practically  stopping  the  loom. 
The  manufacturer  at  once  reached  the  conclusion  that  the 
silk  was  lousy  and  prepared  to  lodge  a  claim  against  the 
raw  silk  dealer  from  whom  this  lot  had  been  purchased. 
Indeed,  careful  examination  of  the  fiber  under  the  micro- 
scope revealed  characteristic  nests  of  fibrillse.  This  evi- 
dence, otherwise  conclusive,  was  offset  by  the  fact  that 


30    CHEMICAL  ASPECTS   OF  SILK  MANUFACTURE 

some  of  the  same  lot  of  silk,  dyed  three  or  four  days  previ- 
ous to  the  trouble,  was  satisfactory  in  all  respects.  The 
mill  experiencing  the  trouble  does  its  own  throwing  as 
well  as  dyeing. 

In  view  of  the  fact  that  part  of  the  silk  was  all  right, 
the  writer's  investigations  led  him  to  the  dye-house  of  the 
mill.  Here  it  was  discovered  that  a  thick  scum  was  form- 
ing on  the  boiled-off  liquors  used  for  dyeing.  It  was 
learned  that  this  liquor  was  from  the  strip  of  some  silk 
received  from  the  throwing  department  only  two  days 
before,  and  that  the  silk  complained  of  had  been  dyed  on 
this  liquor,  although  it  had,  of  itself,  yielded  a  perfect 
gum  soap  when  stripped.  Here  then  was  the  clue  to  the 
mystery.  Analyses  of  the  scum  on  the  gum  soap  showed 
the  presence  of  considerable  petroleum  oil,  which  must 
have  been  in  the  fiber  of  the  second  lot  of  silk.  This  oil, 
in  the  stripping  bath,  held  in  suspension  considerable  fat 
soap.  The  silk  subsequently  dyed  in  this  liquor,  upon 
being  washed  with  the  customary  hard  water,  became 
charged  with  lime  and  magnesia  soaps  which  caused  the 
mischief.  Analysis  of  the  fuzz  scraped  off  in  the  loom 
showed  this  to  consist  entirely  of  such  metallic  soaps. 
The  crowning  piece  of  evidence  was  obtained  in  the  admis- 
sion of  the  head  of  the  throwing  department  that  he  had 
sought  to  reduce  expenses  by  purchasing  cheaper  neats- 
foot  oil.  This  oil  proved  to  be  badly  adulterated  with  petro- 
leum oil. 

It  is  readily  seen  that,  had  the  dyeing  been  done  outside 
of  the  mill,  the  dyer  would  have  been  made  responsible 
for  a  defect  for  which  he  was  in  no  wise  to  blame,  and 
would  doubtless  have  been  mulcted  of  a  large  sum  in 
settlement  of  the  "  claim."  How  many  claims  of  this  kind 
are  charged  •  to  the  dyer  in  the  course  of,  say,  a  year? 
And  who,  in  reality,  is  responsible  for  the  trouble? 


CHAPTER  IV 
SILK   BLEACHING 

THE  bleaching  of  true  or  Bombyx  silk  has  for  its  object 
the  elimination  of  the  last  trace  of  color  left  after  stripping, 
in  order  that  an  absolutely  pure  white  silk  may  be  pro- 
cured. White-dyeing  is  effected  simply  by  working  the 
silk  in  a  rich  bath  of  fresh  soap  to  which  just  a  spot  or 
touch  of  blue  dyestufT  has  been  added.  The  infinitesimal 
quantity  of  the  blue  that  attaches  itself  permanently  to 
the  fiber  suffices  to  produce  a  white  thread.  For  certain 
silk,  it  is  not  necessary  to  bleach  before  dyeing.  Others, 
again,  must  be  bleached  if  a  good  white  is  to  result.  Silks 
that  do  not  strip  absolutely  clear  require  considerable 
blue  to  nullify  the  yellow  or  cream  tinge  that  remains 
after  stripping,  with  the  result  that  they  retain  a  bluish 
cast  which  is  undesirable. 

Since  time  immemorial,  the  bleaching  agent  for  silk 
has  been  sulphur,  inasmuch  as  the  reducing  action  of  its 
fumes  has  qualified  it  as  best  adapted  to  the  removal  of 
the  organic  coloring  matter  in  the  fiber.  Its  use  has  been 
attended  by  one  disadvantage,  to  wit,  that,  since  it  bleaches 
by  reduction,  i.e.,  by  the  removal  of  oxygen,  unless  reduc- 
tion is  complete,  some  traces  of  the  color  may  return 
upon  subsequent  exposure  of  the  silk  to  the  oxidizing 
action  of  the  air.  Before  the  advent  of  the  modern  per- 
oxides, however,  the  oxidizing  treatment  of  silk  for  bleach- 
ing was  impractical,  owing  to  the  fact  that  chlorine  gas, 
the  only  oxidizing  bleach  previously  known,  could  not 
be  employed  because  of  its  drastic  solvent  action  on  the 
thread, 

31 


32    CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

STOVING.  —  The  treatment  of  silk  by  stoving  is  now 
practically  obsolete.  The  silk  skeins,  dampened  to  the 
requisite  degree,  were  hung  on  poles  in  a  chamber  which 
permitted  of  sealing.  In  the  center  of  the  room  stood  a 
small  stove  in  which  the  sulphur  was  burned,  the  resultant 
fumes  permeating  the  fiber.  The  process  suffered  the 
disadvantage  of  being  incapable  of  regulation  and  more 
times  than  not  the  silk  was  over-bleached  and  the  thread 
tendered. 

THE  SULPHUROUS  ACID  PROCESS.  -  -  The  modern 
sulphurous  acid  method  of  bleaching  is  merely  an  amplifica- 
tion of  the  old  stoving  practice,  yet  a  distinct  improve- 
ment over  the  latter  in  that  it  eliminates  all  guess  work. 
In  the  former,  as  in  the  latter  method,  sulphur  is  still 
burned  in  a  small  stove,  but  the  fumes,  instead  of  being 
permitted  to  react  directly  upon  the  silk,  are  conducted 
through  water  contained  in  a  rectangular  wooden  vat,  in 
order  to  produce  a  solution  of  sulphurous  acid  of  a  known 
degree  of  strength.  In  this  bath,  the  silk  is  worked  on 
sticks,  being  turned  until  the  requisite  state  of  color-dis- 
charge has  been  achieved.  In  this  way  it  is  possible  to 
control  the  process  completely. 

HYDROGEN  AND  SODIUM  PEROXIDES  —  TUSSAH  BLEACH- 
ING. —  The  peroxides  of  hydrogen  and  sodium  constitute 
satisfactory  media  for  the  bleaching  of  all  silks  in  place 
of  sulphurous  acid,  but  owing  to  their  increased  cost  over 
the  latter  are  not  used  extensively  for  the  purpose.  On 
the  other  hand,  without  them  it  would  be  impossible  to 
bleach  Tussah.  Attention  has  already  been  directed  to 
the  peculiar  tenacity  of  the  coloring  principle  of  the 
fiber  spun  by  the  Antheria  family;  yet,  because  of  its 
cheapness  compared  with  true  silk  and  because  of  the 
size  of  the  thread,  Tussah  makes  a  most  desirable  filler 
for  woven  fabrics.  It  was  not,  however,  until  the  advent 


SILK  BLEACHING  33 

of  the  peroxides  of  hydrogen  and  sodium  and  their  cost 
reduction  within  commercial  limits,  that  Tussah  bleach- 
ing became  an  accomplished  fact. 

A  peculiarity  of  Tussah,  not  known  to  the  average,  is 
that,  once  brought  into  contact  with  a  soap  solution,  its 
coloring  matter  is  rendered  absolutely  permanent,  and  all 
attempts  at  subsequent  bleaching  are  unavailing.  Accord- 
ingly, instead  of  being  stripped  on  soap,  Tussah  is  stripped 
on  a  bath  of  silicate  of  soda,  containing  25%  of  silicate, 
based  on  the  weight  of  the  silk  manipulated.  The  small 
amount  of  gum  once  removed,  the  silk  is  bleached  by 
means  of  sodium  peroxide  or,  if  the  Tussah  is  old  stock, 
by  means  of  hydrogen  peroxide. 

The  rapidity  with  which  these  peroxides  give  up  their 
oxygen  has  led  to  a  modification  of  the  original  method 
of  using  them.  In  the  latest  practice,  the  bath  consists 
of  sulphate  of  magnesia  (Epsom  salt)  to  which  sulphuric 
acid  and  then  the  peroxide  have  been  added.  The  result- 
ant magnesium  peroxide  is  easier  of  regulation  than  the 
sodium  or  hydrogen  peroxide,  giving  up  its  oxygen  more 
slowly  and  producing  more  uniform  results.  In  bleach- 
ing Tussah  piece  goods,  the  same  methods  obtain  and, 
occasionally,  through  faulty  practice,  tiny  holes  are  burned 
in  the  goods. 

Again,  unless  all  traces  of  the  silicate  of  soda  are  re- 
moved from  the  thread  after  stripping,  the  fibers  are  apt 
to  stick  together  and  prevent  good  winding.  Indeed,  the 
dyed  material  is  apt  to  exhibit,  under  these  circumstances, 
a  chalky  excrescence,  making  the  dyeing  uneven  and 
coming  off  in  a  powder  in  the  looms,  clogging  the  harness 
reeds. 

The  incomplete  removal  of  silicate  of  soda  after  weight- 
ing is  the  direct  cause  of  chalky  threads.  It  is  to  the 
dyer's  advantage  to  use  his  baths  over  and  over  again 


34    CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

as  many  times  as  possible.  Under  proper  strengthening 
and  correction  this  is  feasible  with  the  tin  and  with  the 
phosphate  bath;  but  the  silicate  bath,  once  it  " breaks" 
or  becomes  milky,  must  be  thrown  away.  The  careful 
dyer  sees  to  this  regularly,  but  his  less  careful  brethen, 
actuated  by  a  spirit  of  economy,  at  times  keep  on  using 
" broken"  silicate,  with  the  result  that  a  chalky  condition 
of  the  thread  ensues. 

The  bleach-house  of  a  dyeing  plant  is  maintained, 
wherever  possible,  in  a  building  separate  from  the  main 
works.  In  addition  to  bleaching  silk  the  sulphurous  acid 
bath  is  frequently  used  for  the  preparation  of  souple,  as 
described  in  the  preceding  chapter.  In  those  plants 
where  it  has  been  impossible  to  separate  the  sulphuring 
room  from  the  main  buildings,  the  dyeing  work  has  at 
times  suffered  the  handicap  of  being  subjected  to  the 
fumes  of  sulphur,  which  escape  from  the  room  occasion- 
ally. It  is  at  times  possible  to  account  for  spottiness  in 
dyeing  in  this  way. 

INFLUENCE  OF  STRIPPING  ON  BLEACHING.  —  To  say 
that  unless  stripping  is  complete,  bleaching  will  be  unsat- 
isfactory, is  to  cite  an  axiom.  Indeed,  unless  the  materials 
employed  in  the  cocoon  reeling  and  throwing  are  of  such 
solubility  as  to  insure  their  complete  removal  in  the 
stripping  bath,  defects  of  the  fiber  must  be  created  in 
the  course  of  sulphuring  the  silk. 

Where,  as  is  too  often  the  case,  the  materials  alluded  to 
are  cheap  and  greasy  substitutes  for  soap,  containing 
various  percentages  of  mineral  oil;  or  where,  as  frequently 
occurs,  the  throwster  employs  a  stripping  soap  contain- 
ing an  excess  of  unsaponified  fats,  these  remain  in  the 
fiber  after  stripping,  and  once  subjected  to  the  action  of 
the  sulphurous  acid  become  permanently  embedded  in 
the  silk. 


SILK  BLEACHING  35 

This  is  the  main  cause  of  uneven  bleaching  and,  in 
turn,  of  uneven  dyeing.  Where  such  silk  is  weighted 
after  bleaching  and  before  dyeing,  these  defects  are  radi- 
cally augmented  and  will  account  for  many  of  the  com- 
mon complaints  as  regards  the  finished  silk,  which  the 
reader  will  find  enumerated  in  Chapter  V.  In  this  stage 
of  silk  treatment,  as  in  all  the  others,  eternal  vigilance 
is  the  price  of  safety.  It  is  again  to  be  remarked  that, 
once  the  purity  of  the  raw  and  thrown  silk  is  assured,  the 
chances  are  most  overwhelmingly  in  favor  of  securing  a 
satisfactorily  weighted  and  dyed  thread.  It  is  to  be  noted 
that  the  dyer,  although  capable  of  erring,  seldom  actually 
errs  in  his  treatment  of  the  silk.  It  is  in  reality  the  manu- 
facturer's carelessness  and  neglect  that  are  primarily 
responsible  for  defects  in  dyed  silk. 


CHAPTER  V 
SILK    WEIGHTING 

WEIGHTED  vs.  PURE  DYE  SILKS.  —  Many  distributors 
of  silk  contend  that  silk  weighting  is  tantamount  to  adul- 
teration. It  must  be  conceded  that  where  the  modern 
weighting  process  is  improperly  or  imperfectly  carried  out, 
there  is  some  foundation  for  this  contention.  On  the 
other  hand,  where  the  process  is  properly  effected  the 
silk,  so  far  from  being  adulterated,  is  actually  improved. 
The  increasing  popularity  of  mixed  fabrics,  the  stability  of 
silks  woven  in  the  piece  and  dyed  pure,  the  periodic  recur- 
rence of  the  depression  of  the  market  for  goods  woven 
from  the  treated  skein,  are  perhaps  responsible  for  the 
advocacy  of  the  adulteration  theory.  Its  advocates,  how- 
ever, are  either  ignorant  of  or  overlook  the  fact  that 
mixed  goods  are  as  far  from  being  pure  fiber  as  tin-weighted 
silks.  The  cotton  which  enters  into  the  composition  of 
the  former  is  radically  treated  in  the  spinning  and  in  the 
dyeing.  Not  only  does  it  receive  augumentation  in  the 
slashing  through  the  agency  of  tallow,  starch,  and  talc 
or  allied  ingredients,  but  it  is  also  frequently  treated  with 
muriate  of  tin  in  the  dyeing,  which,  ostensibly  a  mordant 
for  certain  of  the  colors,  is  nevertheless  effective  as  a 
weighting  medium.  Similarly,  woolen  yarns  may  be 
bulked  by  complex  treatment  frequently  applied. 

It  would  seem,  then,  that  the  treatment  applied  to  a 
fiber  to  impart  desirable  properties  has  little  or  nothing 
to  do  with  the  marketability  of  the  fabric  woven  there- 
from, provided  the  treatment  is  carried  out  intelligently. 

3Q 


SILK  WEIGHTING  37 

And  it  will  further  be  seen  that  the  intelligent  treatment 
of  silk  in  this  respect  is  dependent  upon  certain  factors  not 
within  the  control  of  the  dyer,  but  strictly  within  control 
of  the  manufacturer. 

The  very  term  "pure  dye"  is  a  misnomer.  Colored 
silks  of  this  class  indeed  contain  nothing  but  the  silk 
fiber  plus  the  dye.  Pure  dye  blacks  and  some  darker 
colors  are  in  reality  weighted  silks,  albeit  the  weighting 
is  effected  with  substances  other  than  tin  or  the  deriva- 
tives of  tin,  and  they  are  not  so  heavily  weighted  as  the 
"dynamited"  silks.  In  preparing  pure  dye  silks,  advan- 
tage is  taken  of  the  affinity  of  the  silk  fiber  for  tannin, 
and  they  are  accordingly  processed  by  means  of  galls, 
sumac,  etc.,  which  not  alone  form  the  mordant  for  the 
old-fashioned  dyestuffs  still  in  vogue  for  this  class  of  work, 
but,  by  increasing  the  bulk  of  the  silk,  impart  to  it  a 
handle  without  which  it  would  be  practically  unsalable. 
Black  pure  dyes  are  processed  with  the  salts  of  the  metal 
iron,  by  means  of  which  the  silk  is  made  to  absorb 
far  more  tannin  than  it  is  ordinarily  capable  of  doing; 
and  on  this  mordant,  iron  tannate,  the  desired  black 
is  produced.  Wash  silks,  classified  as  pure  dyes,  are  in 
reality  weighted  to  a  limited  extent  through  the  agency 
of  the  chromium  salts  employed  as  a  mordant  for  the 
alizarin  colors  employed  to  dye  them. 

It  is  many  years  since  it  was  first  conceded  that  silk 
does  not  make  a  desirable  woven  fabric  unless  it  is  sub- 
jected to  processes  tending  to  increase  certain  character- 
istics. Since  the  proper  weighting  of  the  silk  assuredly 
increases  its  luster,  handle,  and  elasticity,  it  cannot  be 
legitimately  regarded  as  adulteration. 

OLDER  METHODS.  —  The  above-described  methods  for 
the  production  of  pure  dye  silks  were  formerly  in  general 
vogue,  and  then,  as  now,  relied  upon  to  impart  factitious 


38    CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

weight  to  the  fiber.  For  colors,  they  were  superseded  by 
the  forerunner  of  the  present  " dynamite"  process,  which 
consisted  in  treating  the  silk  with  ammonio-stannate,  or 
pink  salt  as  it  was  better  known,  a  preparation  of  tin 
which  was  subsequently  modified  within  the  fiber.  Since 
the  process  is  now  obsolete,  it  need  not  be  discussed  here. 

Before  passing  to  a  description  of  the  weighting  process 
now  in  use  at  all  of  our  dye-houses,  it  is  necessary  to  point 
out  that  the  influence  of  silk  weighting  has  proven  perni- 
cious, chiefly  in  that  it  has  been  responsible  for  attempts, 
from  time  to  time,  on  the  part  of  the  throwster  to  obtain 
a  factitious  clearance  by  subjecting  the  silk  to  certain  of 
the  baths  employed  in  the  weighting  process.  This  has 
introduced  factors  exercising  a  decidedly  adverse  influ- 
ence on  the  proper  degumming  and  weighting  of  the  silk; 
and  for  some  strange  reason  the  responsibility  for  these 
factors  has  been  attributed  to  the  dyer's  carelessness 
rather  than  to  the  throwster's  malpractice. 

THE  " DYNAMITE"  PROCESS.  —  So  much  depends  upon 
the  proper  weighting  of  the  silk,  and  so  closely  are  the 
previous  processes  to  which  the  silk  is  subjected  inter- 
linked with  its  success,  that  I  feel  justified  in  appending 
here  an  exposition  of  the  theory  of  silk  weighting  in 
addition  to  the  very  necessary  description  of  the  modus 
operandi  of  the  process.  Chemists  differ  radically  in  their 
opinions  of  the  changes  undergone  by  the  silk  fiber  in 
the  course  of  weighting,  and  there  is  much  to  support 
each  theory  advanced.  To  Mr.  George  H.  Hurst,1  the 
English  silk  expert,  belongs  the  credit  of  advancing  the 
most  rational  explanation  of  all,  which  I  now  outline. 

Silk  is  weighted  by  means  of  bichloride  of  tin,  which  is 
in  reality  stannic  chloride  of  the  formula  SnCl4,  which  is 

1  Silk  Dyeing,  Printing  &  Finishing,  by  G.  H.  Hurst.  (Scott,  Green- 
wood &  Co,,  London.) 


SILK  WEIGHTING  39 

subsequently  converted  into  phosphate  and  then  silico- 
phosphate  of  tin,  by  means  first  of  a  bath  of  phosphate  of 
soda  and  then  one  of  silicate  of  soda.  Before  this  con- 
version takes  place,  however,  the  stannic  chloride  is 
reduced  by  the  silk  itself  to  stannous  chloride  of  the  formula 
SnCl2.  Attention  is  particularly  called  to  this  reduction 
as  it  is  the  basic  principle  of  silk  weighting.  Silk  itself 
possesses  the  chemical  property  of  reducing  a  higher  form 
of  chemical  salt  to  a  lower  form. 

Were  it  not  necessary  to  employ  a  complex  chemical 
salt  to  be  reduced  by  the  silk  to  a  lower  form  as  above 
illustrated,  such  substances  as  chloride  of  barium  could  be 
employed.  This  latter  may  be  converted  into  a  silico-phos- 
phate  of  transparency  equal  to  that  of  tin  silico-phosphate. 
It  is  to  be  noted,  however,  that  the  barium  chloride  does 
not  stay  on  the  fiber  and  hence  gives  no  basis  for  weight, 
whereas  bichloride  of  tin  or  any  higher  chloride  of  any 
metal  such  as  iron  or  chromium  which  may  be  reduced  by 
the  silk  to  the  lower  form  of  chloride  does  remain  in  the 
fiber  in  its  reduced  form.  The  chlorides  of  iron  and 
chromium,  however,  impart  a  direct  color  to  the  silk  and 
hence  cannot  be  used  for  weighting  save  for  very  dark 
shades  or  blacks.  Accordingly,  the  only  available  com- 
mercial salt  for  this  purpose  is  the  higher  chloride  of  tin. 

It  is  thus  seen  that  the  silk  fiber,  so  far  from  being  inert, 
possesses  marked  chemical  characteristics.  In  addition 
to  the  reducing  power  above  outlined,  silk  of  itself  con- 
tains a  nitro  group  which  permits  of  .the  diazotation  and 
development  of  certain  shades  on  the  fiber,  without  first 
dyeing  it  with  a  color  that  permits  of  diazotation  as  is 
the  case  with  cotton  and  wool.  Chemical  activity  is  not 
confined  to  silk  among  the  textile  fibers;  both  cotton  and 
wool  exhibit  marked  characteristics  upon  treatment  with 
certain  reagents;  but  it  is  to  be  noted  that  the  latter 


40    CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

permit  of  more  drastic  treatment  than  silk,  because  they 
are  hardier  constitutionally. 

WEIGHTING  FOR  COLORS.  —  A  bath  of  tin  bichloride  is 
prepared  of  a  strength  30°  Be.  This  bath  is  kept  con- 
stantly at  a  temperature  of  60°  F.  In  this  the  silk  is 
immersed  for  one  hour.  It  is  then  removed,  whizzed  in  a 
hydro-extractor  in  order  to  recover  the  excess  of  tin  solu- 
tion, which  is  returned  to  the  main  bath  and  the  silk  is 
then  washed  on  a  suitable  machine.  This  washing  is  not 
merely  for  the  purpose  of  removing  any  excess  of  tin 
solution  that  has  not  been  whizzed  off.  The  water  has 
a  definite  chemical  action  on  the  tin  in  the  fiber,  reducing 
it  to  the  form  of  hydrate,  which  is  subsequently  converted 
to  the  form  outlined  above  by  the  phosphate  and  silicate 
baths. 

At  this  juncture  the  silk  is  again  immersed  in  the  tin 
bath  or  not,  according  to  the  weight  desired.  It  is  to 
be  noted  that: 

To  secure  16-18  oz.  the  silk  is  given  one  bath  of  tin,  one 
bath  of  phosphate,  and  one  bath  of  silicate,  with  suitable 
washings  in  between  and  after  the  various  baths. 

To  secure  18-20  oz.  the  silk  is  given  one  hour  in  tin, 
then  washed,  then  one  hour  in  phosphate,  then  washed, 
then  again  an  hour  in  the  tin,  then  washed,  again  an  hour 
in  the  phosphate,  then  washed,  and  finally  one  hour  in  the 
silicate  of  soda,  after  which  it  is  suitably  soaped  and  finished 
as  noted  below. 

To  secure  22-24  oz.  the  silk  is  given  one  hour  in  tin, 
washed,  one  hour  in  phosphate,  washed,  one  hour  in  tin, 
washed,  one  hour  in  phosphate,  washed,  a  third  hour  in 
tin,  washed,  a  third  hour  in  phosphate,  washed,  and  finally 
one  hour  in  the  silicate,  after  which  it  is  soaped  and  fin- 
ished. 

The  phosphate  bath  employed  in  weighting  stands  at 


SILK  WEIGHTING  41 

a  strength  of  about  6°  Be.,  and  is  heated  to  about  140°  F. 
The  silicate  of  soda  bath  is  made  to  the  same  strength  as 
the  phosphate  bath  and  utilized  at  practically  the  same 
temperature. 

After  the  silk  has  been  treated  with  silicate  of  soda,  it 
is  worked  on  a  rich  soap  bath  for  one  hour  at  150°  F.,  for 
the  purpose  of  removing  all  silicate.  It  is  then  washed 
at  least  twice  on  warm  water  and  the  last  trace  of  soap 
removed  by  treatment  with  water  containing  a  small  per- 
centage of  acid. 

Were  the  weighting  confined  to  the  form  of  tin  silico- 
phosphate,  far  less  danger  would  accrue  to  the  process 
than  is  normally  experienced.  Unfortunately,  through 
the  persistent  demands  of  the  manufacturer  for  a  big 
thread,  other  ingredients  enter  into  the  weighting  of  the 
fiber.  For  example,  sulphate  of  alumina,  although  not 
so  much  in  vogue  now  as  formerly,  is  successfully  employed 
for  reducing  the  number  of  " passes"  necessary  to  pro- 
duce a  given  weight.  Through  its  use  it  is  possible  to 
obtain: 

20  oz.  full  in  one  pass,  i.e.,  1  tin,  1  phosphate,  1  alumina, 
1  phosphate,  and  1  silicate. 

24  oz.  full  in  two  passes,  i.e.,  1  tin,  1  phosphate,  1  tin, 
1  phosphate,  1  alumina,  1  phosphate,  and  1  silicate. 

If  the  reader  will  compare  these  figures  with  those  given 
above  for  obtaining  similar  weights  with  just  tin,  phos- 
phate, and  silicate,  the  saving  of  materials  will  be  seen. 

Thus,  to  obtain  24  oz.  full  normally  presupposes: 

3  hours  in  the  tin  bath 

3  hours  in  the  phosphate  bath 

1  hour  in  the  silicate  bath 

1  hour  in  the  soap 

5  hours  for  the  various  washings 


42    CHEMICAL  ASPECTS   OF  SILK  MANUFACTURE 

or  a  total  of  13  hours,  whereas,  to  obtain  the  same  weight 
using  sulphate  of  alumina  we  require: 

2  hours  in  the  tin  bath 

3  hours  in  the  phosphate  bath 
1  hour  in  the  alumina  bath 

1  hour  in  the  silicate  bath 

1  hour  in  the  soap 

5  hours  for  the  various  washings 

or  a  total  of  13  hours. 

It  will  be  seen  that  while  the  use  of  the  alumina  saves 
neither  time  nor  labor,  it  results  in  the  saving  of  tin,  the 
most  expensive  ingredient  in  the  process,  by  reducing  the 
required  number  of  tin  immersions.  Another  advantage 
is  the  increase  in  the  size  of  the  thread  through  its  use. 

Sulphate  of  alumina  has  been  more  recently  superseded 
by  sulphate  of  zinc  and  in  rare  instances  chloride  of  zinc, 
although  the  use  of  the  last  named  is  exceedingly  danger- 
ous, owing  to  its  solvent  action  on  the  silk.  In  order 
that  the  fiber  may  withstand  the  burden  imposed  by  these 
extra  treatments,  it  is  customary  to  incorporate  a  certain 
amount  of  glue,  or  better,  casein  with  the  phosphate  of 
soda  bath,  which  serves  to  "re-animalize"  the  fiber. 

WEIGHTING  FOR  BLACKS.  —  The  weighting  in  black 
organzine  as  well  as  in  black  souple  is  not  effected  by 
means  of  tin.  On  the  other  hand,  the  weighting  in  black 
tram  is  part  tin  and  part  tannin.  Thus,  to  produce  a 
black  tram  weighing  32  oz.,  we  proceed  as  follows: 

24  oz.  weight  are  put  in  by  means  of  tin,  that  is  to  say, 
the  silk  receives  three  tins  and  three  phosphates  and  finally 
the  silicate.  After  the  silk  has  been  finished  from  the 
silicate,  it  is  either  immersed  over  night  in  a  bath  of  gam- 
bier  of  about  8°  Be.  strength,  or  it  is  slowly  worked  for 
ten  hours  in  such  a  bath,  starting  with  the  bath  at  180°  F. 


SILK  WEIGHTING  43 

and  allowing  it  to  cool  gradually  as  the  silk  is  worked. 
Not  only  does  the  gambier  put  in  the  additional  8  oz. 
weight  required,  but  it  also  forms  the  basis  for  the  black, 
and  for  this  reason  there  is  incorporated  with  the  bath 
about  2%  of  ordinary  sulphate  of  iron  or  copperas,  which 
forms  a  mordant,  tannate  of  iron.  Tin  crystals  are  some- 
times employed  to  force  the  weight.  After  the  treat- 
ment with  the  gambier,  the  silk  is  suitably  soaped  and 
washed  and  is  then  dyed  on  a  bath  containing  100%  of 
soap  and  from  25%  to  40%  of  hsematine  (logwood). 
This  combines  with  the  tannate  of  iron  in  the  silk  fiber 
to  form  what  is  practically  an  ink,  which  is  the  required 
black. 

Black  organzine  and  black  souple,  however,  are  weighted 
and  dyed  by  the  following  process.  The  basic  weighting 
material  is  copperas  nitrate  of  iron,  popularly  known  as 
red  iron.  This  is  made  up  into  a  bath  of  about  30°  Be. 
and  is  used  much  the  same  as  the  tin  bath.  That  is  to 
say,  the  silk  is  given  one  or  more  immersions  in  the  red 
iron  according  to  the  weight  desired.  Between  each 
immersion  in  the  red  iron,  the  silk  is  properly  soaped. 
The  next  step  is  what  is  known  as  blue-bottoming.  This 
consists  of  treating  the  silk  which  has  been  immersed  in 
the  red  iron  to  a  suitable  bath  of  ferrocyanide  of  potassium, 
commonly  known  as  the  yellow  prussiate  of  potash.  This 
combines  with  the  iron  to  form  the  color  known  as  Prussian 
blue.  The  silk,  after  blue-bottoming,  is  dyed  on  a  .bath 
of  soap  and  logwood  similar  to  that  employed  for  black 
tram.  The  blacks  so  produced  may  be  further  improved 
by  topping  with  a  black  anilin  dye. 

INFLUENCE  OF  PRIOR  PROCESSES  ON  WEIGHTING.  — 
The  above  exposition  of  the  essentials  of  the  methods  of 
silk  weighting  will  be  of  use  to  the  reader  only  if  he  pauses 
to  review  and  consider  the  possible  detrimental  effects 


44    CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

which  may  ensue  through  the  weighting  of  the  silk,  be- 
cause of  his  neglect  to  become  acquainted  with  its  initial 
characteristics.  Unless  the  silk  is  in  good  shape  at  the 
outset  it  will  turn  out  poorly.  It  is  undoubtedly  true 
that  much  of  the  responsibility  for  the  ultimate  good 
quality  of  the  silk  devolves  upon  the  dyer.  On  the  other 
hand,  it  must  not  be  overlooked  for  a  moment  that  an 
equal  measure  of  responsibility  devolves  upon  the  owner 
of  the  silk,  with  which  responsibility  it  is  manifestly 
unfair  to  burden  the  dyer  in  addition  to  his  own. 

The  major  defects  complained  of  in  dyed  and  finished 
silk  are: 

1.  Weakness  of  thread. 

2.  Shadiness  of  the  color. 

3.  Absence  of  adequate  luster. 

4.  Poor  winding  qualities,  such  as  stickiness. 

5.  Chalkiness  and  brittleness  of  the  thread. 

These  are  the  defects  commonly  complained  of.  The 
question  logically  arises,  is  the  responsibility  for  these 
defects  entirely  the  dyer's?  Not  necessarily.  It  is  abso- 
lutely true  that  the  dyer  working  on  silk  of  good  quality 
which  has  been  properly  treated  in  the  throwing  may, 
through  his  carelessness  in  carrying  out  the  various  weight- 
ing processes  or  in  attempting  new  and  experimental  treat- 
ments, utterly  ruin  the  silk.  With  this  in  view,  the  Silk 
Association  of  America  has  formulated  stringent  rules 
affecting  the  acceptance  or  rejection  of  dyed  silks.  It  is 
equally  true  that  the  dyer  may  without  error  carry  out 
the  processes  required  for  the  production  of  the  weight 
ordered  by  the  manufacturer  and  yet  the  silk  be  anything 
but  acceptable.  Whence  arises  the  cause  of  this  latter 
contingency?  Is  the  responsibility  for  making  or  marring 
the  quality  of  the  silk  entirely  the  dyer's?  Let  us  see. 

We  have  already  seen  that,  in  the  initial  reeling  of  the 


SILK  WEIGHTING  45 

thread  from  the  cocoon,  it  is  possible  to  employ  softening 
media  which  may  impart  a  factitious  bulk  to  the  thread. 
The  soaps  employed  for  the  softening  of  the  cocoon  at 
times  contain  petroleum  oil.  If  we  assume  such  to  be 
the  case  for  the  purpose  of  a  hypothetical  illustration,  we 
may  then  trace  the  behavior  of  the  thread  through  sub- 
sequent operations.  No  adverse  factor  will  be  noticeable 
until  such  time  as  the  thread  reaches  the  dyer  to  be  de- 
gummed.  The  presence  of  the  mineral  oil  in  the  fiber 
will  account  for  the  holding  in  suspension,  within  the 
fiber,  of  a  proportion  of  the  soap  from  the  degumming 
bath,  which  suspended  soap  does  not  wash  out.  The  silk 
will  then  enter  the  tin  bath  where  the  metal  will  immedi- 
ately combine  with  the  fat  of  the  soap  to  form  an  insoluble 
tin  soap,  sticky  and  greasy,  which  is  further  accentuated 
as  the  silk  passes  through  the  subsequent  weighting  baths. 
The  result  may  be  any  or  all  of  the  above  outlined  com- 
plaints. It  may  result  not  only  in  the  tendering  of  the 
thread  in  spots,  but  will  account  for  much  of  the  sticki- 
ness at  times  experienced  in  winding  as  well  as  shady 
dyeing.  The  exact  results  of  the  presence  of  certain 
impurities  originating  in  the  initial  processes  of  silk  treat- 
ment have  already  been  outlined  in  the  discussion  of  the 
so-called  lousiness  of  silk  under  Chapter  III.  In  view  of 
the  fact  that  silk  treatment  consists  of  closely  interlinked 
processes,  the  success  of  each  dependent  upon  the  proper 
effectment  of  the  preceding,  the  author  feels  justified  in 
constantly  reverting  to  the  possibility  of  the  introduction 
of  defects  at  stages  before  the  silk  reaches  the  dyer. 

If  the  manufacturer  would  take  the  trouble  to  have  his 
raw  silk  or  thrown  silk  assayed,  many  of  the  difficulties  of 
silk  weighting  would  be  minimized.  The  writer  does  not 
exaggerate  when  he  states  that  in  those  mill  dye-houses 
^where  no  baths  are  employed  other  than  the  customary 


46    CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

tin,  phosphate,  and  silicate,  and  where  all  materials  includ- 
ing the  raw  silk  are  subject  to  proper  supervision,  "  dyna- 
mite" results  may  be  safely  guaranteed  for  two  if  not 
for  three  years.  If  this  can  be  brought  about  in  one  class 
of  dye-house,  there  is  absolutely  no  reason  why  it  should 
not  be  brought  about  in  all.  That  it  is  not  brought  about 
is  due  more  to  the  manufacturers'  utter  disregard  of  ele- 
mentary principles  than  to  any  carelessness  on  the  part 
of  the  dyer.  The  dyer's  duty  is  to  supply  the  weight 
ordered  by  the  manufacturer  independent  of  the  quality 
of  the  silk  submitted,  and  so  long  as  the  manufacturer 
continues  to  order  heavy  weighting  without  regard  to 
whether  or  not  the  silk  he  submits  can  stand  this  weight- 
ing, so  long  will  complaints  continue.  It  may  be  stated 
without  reserve  that  did  the  manufacturer  acquaint  him- 
self with  the  initial  characteristics  of  his  silk  he  would 
be  enabled  to  so  order  his  dyeing  as  to  permit  him  to 
guarantee,  without  fear,  the  life  of  his  silk  for  a  definite 
period. 


CHAPTER  VI 
SILK  DYEING 

UNLIKE  the  dyeing  of  cotton  and  wool,  silk  dyeing 
does  not  admit  of  the  use  of  exact  formula.  It  is  possible 
to  achieve  a  given  shade  on  the  two  former  through 
the  use  of  just  so  much  dyestuff  per  hundred  pounds 
manipulated  and  by  heating  the  bath  to  an  exact  degree, 
giving  the  goods  a  definite  number  of  turns  and  working 
them  for  a  given  time.  In  silk  dyeing,  however,  apart 
from  certain  fundamental  rules  observed  in  common  by 
dyers,  the  procedure  is  largely  empirical,  demanding  con- 
siderable ingenuity  on  the  part  of  the  operator  and  afford- 
ing a  wide  latitude  for  his  exercise  thereof.  Your  silk 
dyer  must  trust  to  his  eye  for  color,  rather  than  to 
exact  weights  of  materials,  in  order  to  dye  the  goods  to 
shade. 

While  it  is  sought  to  produce  colors  on  cotton  and  wool 
that  are  fast  to  strong  soaping,  no  such  solicitude  enters 
into  the  dyeing  of  silk  save  for  some  few  special  require- 
ments. The  very  nature  of  the  silk  fiber,  together  with 
the  necessity  for  preserving  its  natural  luster,  elasticity 
and  scroop,  precludes  the  drastic  treatments  applied  to 
cotton  and  to  wool  in  dyeing.  Cotton  does  not  suffer 
much  from  prolonged  heating  in  the  dye  bath;  silk  does, 
especially  if  it  has  been  weighted  before  dyeing.  Over- 
working silk  in  the  dye  bath  is  responsible  for  poor  winding, 
assuming  all  other  factors  to  be  normal.  Accordingly,  the 
most  skilful  silk  dyer  is  he  who  obtains  his  shade  with  the 
least  number  of  boils  and  turns,  —  a  condition  which 

47 


48    CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

presupposes  the  absolute  purity  of  the  silk  fiber  as  well  as 
the  proper  effectment  of  processes  prior  to  dyeing. 

COLOR  DYEING.  —  In  the  dyeing  of  any  textile  fiber,  it 
is  necessary  to  distinguish  between  the  coloring  of  the  fiber 
and  true  dyeing.  Immerse  any  fiber  in  a  solution  of  dye- 
stuff,  and  it  will  assume  the  color  of  the  bath  to  a  greater 
or  less  extent,  dependent  upon  the  nature  of  the  fiber  it- 
self. It  does  not  follow,  however,  that  the  fiber  is  dyed 
by  the  operation.  Dyeing,  as  distinguished  from  coloring, 
is  the  more  or  less  permanent  chemical  combination  of 
the  dyestuff  with  the  fiber;  coloring,  the  mere  temporary 
mechanical  permeation  of  the  fiber  by  the  dyestuff. 

Modern  coloring  materials  may  be  roughly  divided  into 
two  general  classes.  A,  basic  or  substantive  colors,  and 
B,  acid  colors.  Class  A  have  the  property  of  combining 
directly  with  certain  fibers  to  form  a  dye,  without  the  aid 
of  an  intermediate  chemical  substance  termed  a  mordant. 
They  are  salts  of  a  coloring  principle  which  behaves  as  a 
base.  Thus,  fuchsine,  a  basic  color,  sometimes  employed 
in  silk  dyeing,  is  the  hydrochloride  of  the  base  pararosani- 
line,  just  as  common  salt  is  the  chloride  of  the  base  sodium. 
Class  B,  on  the  other  hand,  behave  like  acids  and  will  not 
combine  with  the  fiber  without  the  interposition  of  a  third 
basic  substance  or  mordant.  The  behavior  of  these  various 
colors  depends  largely  on  the  fiber  with  which  they  are 
expected  to  combine.  We  are  concerned  solely  with  their 
behavior  towards  silk. 

Both  classes  of  colors  are  adapted  to  silk  dyeing,  although 
few  of  the  basic  are  now  used  except  for  special  work.  The 
earliest  chemical  researches  into  the  dyeing  of  silk  revealed 
the  fact  that  a  bath  containing  a  basic  color  together  with 
a  quantity  of  acetic  acid  could  be  exhausted  of  its  coloring 
matter  by  immersing  sufficient  silk  which  was  permanently 
dyed  thereby.  Prior  to  the  advent  of  the  coal-tar  colors, 


SILK  DYEING  49 

silk  was  dyed  by  means  of  vegetable  coloring  matters  such 
as  logwood,  Brazil  wood,  archil,  safflower,  madder,  etc., 
and  certain  animal  products  such  as  cochineal.  Much 
profit  and  enjoyment  may  be  derived  from  a  perusal  of 
the  treatise,1  first  published  in  1789,  by  three  French 
pioneers  in  the  domain  of  the  chemistry  of  dyeing,  from 
which  the  reader  will  obtain  an  excellent  idea  of  the  diffi- 
culties encountered  in  silk  dyeing  one  hundred  and  twenty 
years  ago.  Although  these  materials  have  been  supplanted 
by  the  coal  tar  dyes,  some  of  the  former  are  still  in  use  on 
special  work;  and  it  is  curious  to  note  that  while  modern 
machinery  has  greatly  simplified  the  problem,  the  essen- 
tials of  silk  dyeing  are  the  same  to-day  as  they  were  then. 

As  has  already  been  pointed  out,  of  late  years  the  acid 
colors  have  come  into  greater  use  than  the  basic  for  silk 
dyeing,  for  the  reason  that  the  bulk  of  the  silk  now  woven 
is  tin  weighted.  The  use  of  basic  colors  on  top  of  tin  is 
attended  by  numerous  difficulties.  The  tin  silico-phos- 
phate  in  the  weighted  fiber  acts  as  a  partial  mordant  for 
the  acid  colors,  causing  them  to  penetrate  the  fiber  very 
rapidly  in  the  presence  of  sulphuric  acid.  For  silk  printing 
of  certain  kinds,  however,  the  basic  colors  possess  con- 
siderable advantage  over  the  acid  colors. 

One  of  the  great  difficulties  in  silk  dyeing  lies  in  the  fact 
that,  if  the  best  results  are  to  be  obtained,  a  given  shade 
cannot  be  achieved  by  means  of  a  single  dyestuff.  In 
cotton  and  wool  this  is  quite  feasible.  Take,  for  example, 
the  common  pink  cord  with  which  every  one  is  familiar. 
This  shade  may  be  obtained  with  exactitude  time  and  time 
again  by  using  just  so  much  rose  bengal  in  the  dye  bath 
together  with  just  so  much  sodium  sulphate  for  mordant 
and  heating  the  bath  to  a  given  temperature.  To  obtain 

1  Art  of  Dyeing  Silk,  Wool  and  Cotton,  by  M.  Hellot,  M.  Macquer 
and  M.  Le  Pileur  D  'Appligny.  (D.  Van  Nostrand  Co.,  New  York.) 


50    CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

the  same  shade  on  silk  would  require  at  least  two  separate 
colors;  fast  red  for  the  body  of  the  color  and  rhodamine 
for  topping  to  shade.  Indeed,  all  silk  dyeing  is  based  on 
the  combination  of  the  elementary  colors  of  the  solar 
spectrum.  Thus,  browns  are  produced  by  combining 
yellow,  red,  and  green;  grays,  by  combining  weak  blue- 
black  (nigrosine)  with  yellow  and  a  little  red  and  blue. 
Greens  are  obtained  by  combining  blue  and  yellow;  and 
where  green  itself  is  the  basis  of  the  bath,  as  in  olive  shades, 
the  shade  is  rendered  more  blue  or  more  yellow  as  may  be 
required  by  adding  one  or  the  other  of  these  colors  to  the 
dye  bath.  It  is  thus  readily  seen  that,  to  cause  the  proper 
proportion  of  each  color  necessary  to  a  given  shade  to  go 
onto  the  fiber,  is  no  small  matter.  It  is  because  of  this 
difficulty  that  the  dyer  is  afforded  wide  latitude  for  the 
exercise  of  his  ingenuity. 

The  dye  bath  once  prepared  and  brought  to  the  boil, 
the  silk  is  entered  and  given  five  turns.  It  is  then  laid 
up  and  the  bath  reboiled,  when  it  is  re-entered  and  given 
another  five  turns  and  so  on  until  the  silk  is  dyed  to  shade. 
The  skilful  dyer,  assuming  that  all  previous  processes  are 
properly  carried  out,  will  get  the  shade  in  15  turns,  —  that 
is,  three  boils.  A  less  skilful  will  have  to  give  the  silk 
anywhere  from  20  to  30  turns  or  from  4  to  6  boils.  As 
the  dye  bath  for  weighted  silks  invariably  contains  a  slight 
excess  of  sulphuric  acid  added  to  facilitate  the  dyeing,  it 
is  not  difficult  to  comprehend  that  prolonged  working  of 
the  silk  in  dyeing  is  to  be  avoided.  It  interferes  with  the 
winding  of  the  silk,  for  one  thing;  for  another,  it  tends  to 
disturb  the  chemical  balance  of  the  weighting  materials 
in  the  fiber,  with  the  result  that  the  tin  may  subsequently 
oxidize  and  the  woven  silk  rot. 

The  boiled-off  liquor,  containing  the  gum  from  the  strip, 
is  extensively  used  in  dyeing.  It  is  practically  indispen- 


SILK  DYEING  51 

sable  for  dark  shades  on  weighted  silks.  The  tin  salts  in 
the  fiber,  once  the  bath  has  been  broken  with  the  sulphuric 
acid,  tend  to  draw  certain  of  the  colors  too  rapidly  into  the 
fiber,  resulting  in  uneven  dyeing.  The  silk  gum,  on  the 
other  hand,  tends  to  retard  the  absorption  of  the  colors 
by  the  fiber  and  a  medium  rate  of  absorption  is  accordingly 
achieved  by  the  addition  of  a  slight  excess  of  sulphuric 
acid  to  the  bath,  certain  shades  requiring  more  acid  than 
others.  The  boiled-off  liquor  is  used  also  for  pure  dye, 
although  for  this  class  of  work  it  may  be  dispensed  with 
and  a  dye  bath  based  on  sulphuric  acid  and  sulphate  of 
soda  substituted.  Indeed,  where  there  is  a  shortage  of 
gum  soap,  this  same  bath  is  used  for  the  lighter  shades  on 
tin  weighted  silk,  although  the  silk  thus  dyed  has  a  ten- 
dency to  harshness  of  feel. 

Once  the  silk  is  dyed  to  shade,  it  is  washed  several  times 
\jf  with  hard  water  and  then  given  a  bath  of  acetic  acid  to 
restore  the  "  scroop."  Owing  to  the  fact  that  the  bulk  of 
silk  sent  to  be  weighted  and  dyed  is  far  from  pure,  initially, 
with  the  result  that  a  large  number  of  boils  is  required  to 
dye  it  to  shade,  the  silk  becomes  slightly  fuzzy  from  over- 
working and  it  is  then  customary  to  finish  it  with  an  emul- 
sion of  olive  oil,  soda,  and  acetic  acid,  which  serves  to  lay 
the  fuzz  on  the  fiber.  Dyers  avoid  this  treatment  wherever 
possible,  as  the  oil  thus  put  on  the  fiber  deadens  the  scroop 
of  the  silk  and  may  sooner  or  later  sweat  out  in  greasy 
spots  if  used  to  excess.  It  is  not  always  feasible  to  obtain 
the  shade  in  15  turns;  but  where  reasonable  care  is  exer- 
cised, it  may  be  obtained  in  20,  in  which  case  it  is  not 
necessary  to  use  the  above  finishing  emulsion. 

BLACK  DYEING.  —  A  full  description  of  the  processes  in 
vogue  for  this  class  of  work  will  be  found  on  pages  42 
and  43. 

FAST  COLORS.  —  Ordinarily,  dyed  silks  are  not  fast  to 


52    CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

strong  soaping.  In  this  we  have  conclusive  proof  that  the 
tin  salts  in  the  weighted  fiber  act  only  as  a  weak  or  partial 
mordant.  Indeed,  where  silk  weighting  is  properly  done, 
the  combination  of  tin,  phosphate,  and  silicate  is  practically 
inert.  Were  it  otherwise,  it  is  to  be  presumed  that  the 
silk  would  speedily  go  to  pieces  owing  to  the  reversion  of 
the  tin  to  the  form  of  oxide,  in  which  form  it  is  decidedly 
inimical  to  the  life  of  the  fiber.  Hence,  if  the  combination 
is  permanent,  as  it  should  be,  it  is  not  to  be  expected  that 
the  tin  itself  is  free  to  combine  with  the  colors. 

The  production  of  fast  colors  is  confined  to  wash  silks 
(art  embroidery  silks,  etc.)  These  are  dyed  pure  in  so  far 
as  they  are  free  from  tin  weighting.  The  colors  employed 
are  the  alizarin  (artificial  madder)  derivatives  and  these 
are  mordanted  by  means  of  chromium  chloride.  This  class 
of  coloring  material  might  be  used  for  the  production  of 
fast  colors  on  pure  organzine  and  tram;  but  the  number  of 
shades  is  small  and  they  are  apt  to  be  dull  unless  the  silk 
undergoes  special  treatment.  They  are  used  to  advantage, 
however,  in  re-dyeing  ribbons  in  the  piece. 

DEVELOPED  COLORS.  —  Save  for  rare  shades  on  wash  silks, 
this  method  of  dyeing  is  not  practised  in  silk  manufac- 
ture. It  is  worthy  of  limited  mention,  however,  because 
of  its  possibilities.  The  reader's  attention  has  been  sev- 
eral times  directed  to  the  fact  that  silk  contains  a  nitro 
group  which  admits  of  direct  diazotation  and  development. 
Were  it  not  for  the  time  and  labor  involved,  the  dyeing 
by  diazotation  and  development  as  now  practised  for 
cotton  would  assuredly  be  applied  to  silk. 

In  dyeing  by  these  methods,  the  fiber  is  first  dyed  with 
a  color  containing  the  necessary  nitro  group.  This  is 
subsequently  diazotized  by  a  bath  of  sodium  or  potassium 
nitrite  in  hydrochloric  acid.  Finally,  the  fiber  is  placed 
in  a  developing  bath  which  produces  a  shade  utterly  dif- 


SILK  DYEING  53 

ferent  from  the  one  initially  dyed.  Such  colors  are  created 
chemically  within  the  fiber  and  hence  offer  great  resistance 
to  soaping  and  light.  It  may  interest  the  reader  to  learn 
that  many  of  the  highly  praised  blacks  of  European  pro- 
duction are  dyed  by  this  method;  and  in  view  of  the  threat- 
ened competition  with  European  interests  in  the  very  near 
future,  it  is  probable  that  the  American  dyer  will  not  be 
slow  to  adopt  it. 

PIECE  DYEING.  —  The  modus  operandi  of  piece  dyeing 
differs  radically  from  that  of  skein.  Its  success  is  as  much 
dependent  upon  adequate  machinery  for  handling  the 
goods  as  upon  the  chemical  principles  involved,  as  the  latter 
are  not  so  complex  as  in  skein  dyeing.  This  statement, 
however,  holds  good  only'so  long  as  piece  goods  are  dyed 
pure,  which  is  the  case  to  date.  It  is  reported  that  Euro- 
pean dyers  have  recently  perfected  machinery  and  process 
for  weighting  goods  in  the  piece  and  we  shall  doubtless 
ere  long  witness  the  introduction  of  the  method  into  the 
United  States  —  a  possibility  which  is  to  be  sincerely 
deplored. 

Gum  soap  is  seldom  used  in  piece  dyeing.  The  ease 
with  which  the  colors  penetrate  the  woven  fabric,  once 
it  has  been  boiled  off,  whether  the  goods  are  all  silk,  silk 
and  cotton,  silk  and  schappe,  or  silk  and  wool,  permits 
of  dyeing  on  a  bath  of  mixed  acetic  and  sulphuric  acids 
with  the  addition  of  sodium  sulphate. 

In  view  of  the  marked  impurities  of  manufactured  cotton, 
cotton-backs  receive  a  more  drastic  scouring  prior  to 
dyeing  than  could  be  safely  applied  to  all-silks.  Similarly, 
goods  woven  of  silk  and  schappe  or  silk  and  wool  require 
special  treatment  before  dyeing.  It  is  not  within  the 
province  of  this  work  to  deal  extensively  with  the  fer- 
mentation treatments  applied  to  the  various  silk  wastes 
ere  they  can  be  spun  into  a  workable  fiber.  Suffice  it 


54      CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

to  say  that  their  complexity  is  such  as  to  be  responsible 
for  seriously  adverse  chemical  factors  which  must  be 
specially  dealt  with  in  dyeing  goods  containing  schappe. 

In  the  dyeing  of  goods  in  the  piece,  many  processes 
inapplicable  to  skein  dyeing  are  successfully  used.  The 
conditions  obtaining  are  rather  similar  to  those  encountered 
in  cotton  and  wool  dyeing. 

INFLUENCE  OF  PRIOR  PROCESSES  ON  DYEING.  —  Since 
the  boiled-off  liquor  containing  the  silk  gum  is  essential 
to  skein  dyeing,  and  since  all  impurities  entering  into  the 
raw  or  thrown  silk  must  contaminate  the  boiled-off  liquor, 
the  connection  between  cocoon  reeling  as  well  as  throwing 
and  dyeing,  is  readily  seen.  Adulteration  of  the  throw- 
ster's materials  simply  means  trouble  in  the  dyeing  either 
directly  or  through  conditions  arising  from  this  adultera- 
tion in  the  course  of  weighting  the  silk.  This  subject 
must  be  dealt  with  at  length  a  little  further  on;  and  there 
is  hence  no  necessity  for  straining  the  reader's  patience 
with  its  discussion  at  this  juncture. 


CHAPTER  VII 
SILK  FEINTING  AND  FINISHING 

THE  chemical  principles  involved  in  printing  any  textile 
fabric,  like  the  mechanical  principles,  are  very  similar. 
Just  as  in  dyeing,  the  selection  of  the  colors  and  the  prepa- 
ration of  printing  media  are  controlled  by  the  natural 
characteristics  of  the  fiber  to  be  printed.  The  production 
of  the  design  on  rollers  and  the  type  of  machine  used 
for  actual  printing  are  the  same  whether  the  fabric  be 
silk,  cotton,  or  wool.  That  is,  the  basic  principles  are 
the  same;  some  slight  modification  of  the  depth  of  the 
engraved  lines  being  made  in  the  case  of  silk.  The  silk 
fabric  is  somewhat  flimsier  than  the  corresponding  cotton 
or  wool  fabrics,  and  hence  the  printed  design  on  silk  must 
lie  at  the  surface  as  much  as  possible  and  not  bleed  through 
to  the  reverse  side  to  any  extent.  The  secural  of  the 
result  is  dependent  as  much  on  mechanical  factors  as 
chemical. 

As  a  rule,  silk  printing  is  confined  to  fabrics  woven  of 
pure  silk  dyed  in  the  piece,  although  it  is  quite  feasible  to 
produce  designs  on  weighted  silks  woven  from  the  dyed 
skein.  Again,  the  design  is  frequently  printed  upon 
warps  before  weaving.  The  great  latitude  of  silk  print- 
ing procedure  is  responsible  for  the  many  attractive 
novelties  now  on  the  market;  nor  is  the  possibility  of 
producing  new  effects  by  any  means  exhausted,  not  only 
because  of  the  yearly  advent  of  new  colors  permitting  of 
new  treatments  and  effects,  but  because  of  the  great  num- 
ber of  possible  combinations  of  a  given  design. 

55 


56    CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

PRINT  COLORS  AND  THICKENERS.  —  In  printing  all  tex- 
tiles, it  is  sought  to  incorporate  the  color  with  the  fiber 
as  far  as  possible.  In  the  case  of  wall  paper,  this  is  effected 
mechanically  or  physically,  the  glue  used  to  size  the  pulp 
colors  binding  these  to  the  paper.  In  the  case  of  wool, 
cotton,  and  silk,  however,  this  incorporation  is  effected  by 
actually  mordanting  the  colors  within  the  fiber.  Accord- 
ingly, the  colors  chiefly  selected  for  silk  printing  are  the 
basic  colors  described  in  the  last  chapter.  These  are  all 
precipitable  by  means  of  tannic  acid,  and  once  precipi- 
tated are  practically  fast  to  warm  soaping.  It  is  thus 
seen  that,  as  regards  the  selection  of  colors,  silk  printing 
is  the  antithesis  of  silk  dyeing. 

Nor  can  the  aqueous  solution  of  these  colors,  or  of  any 
color  for  that  matter,  be  at  once  applied  to  the  fabric. 
They  must  first  be  thickened  in  order  that  they  will  print 
evenly  from  the  rollers  and  not  merely  splash  over  the 
surface  of  the  silk  and  bleed  in  all  directions  through  the 
goods.  The  thickening  of  the  colors  may  be  accom- 
plished by  means  of  a  number  of  materials.  The  most 
frequently  employed  is  a  high  grade  of  gum  tragacanth, 
a  vegetable  gum  of  considerable  purity,  possessing  the 
property  of  absorbing  a  great  quantity  of  water  in  the 
cold  and  at  the  same  time  dissolving  to  form  a  semi-fluid 
paste.  In  the  best  printing  practice  this  gum  is  used  by 
itself.  Its  high  cost,  however,  frequently  prompts  the 
printer  to  mix  with  it  cheaper  media  such  as  gum  la  biche, 
developed  starches  and  others.  Egg  and  blood  albumin 
are  well  adapted  to  color  thickening,  although  the  dark 
color  of  the  latter  debars  it  from  certain  classes  of  work. 
Both  these  substances  are  closely  allied  in  constitution  to 
silk  itself  and  hence  are  regarded  with  considerable  favor 
as  thickening  media.  Their  preparation  is  attended  by 
certain  difficulties  not  involved  in  the  use  of  gum  traga- 


SILK  PRINTING  AND  FINISHING  57 

canth.  Casein,  derived  from  milk,  is  a  cheap  and  effect- 
ive color  thickener.  It  is  not  used  extensively  because  of 
the  difficulty  of  preserving  its  solution  against  fermen- 
tation. 

The  color  base  or  thickener  prepared,  the  color  itself  is 
added.  Since  absolute  clearness  of  the  colors  is  a  pre- 
requisite of  silk  printing,  and  since  colors  dissolve  to  a 
clearer  solution  in  alcohol  than  in  water,  wood  alcohol  is 
extensively  employed  for  the  purpose.  Next,  a  propor- 
tion of  tannic  acid,  previously  dissolved  in  alcohol,  is 
added  to  the  mass.  This  does  not  at  once  react  with  the 
colors,  but  by  the  time  the  silk  is  printed,  serves  to  mor- 
dant them  upon  the  fiber. 

DIRECT  PRINTING.  —  In  this  mode  of  printing,  the  silk 
is  brought  in  contact  with  the  engraved  rollers  inked  with 
the  colors.  After  the  design  is  on  the  silk,  the  fabric  is 
washed  to  remove  the  color  thickener,  else  the  printed 
portions  would  dry  stiff.  The  silk  is  then  hung  upon  an 
extending  rack  to  dry. 

RESIST  PRINTING.  —  Of  late  years  this  mode  of  printing 
has  not  been  practised  for  silk,  although  commonly  em- 
ployed on  cotton  and  wool.  The  method  is  based  upon 
the  fact  that  the  fiber,  when  impregnated  with  certain 
chemicals,  will  not  take  up  any  color  whatever,  or,  if  the 
resist  materials  be  modified,  will  take  up  only  certain 
colors.  The  design  is  printed  on  the  goods  in  blank,  the 
color  thickener  containing  simply  the  resist  media.  The 
fabric  thus  printed  is  then  dyed  either  in  a  bath  of  a  single 
dyestuff,  when  the  design  does  not  dye  and  the  ground 
alone  assumes  the  color,  or  in  a  dye  bath  of  mixed  colors, 
when  the  ground  assumes  one  shade  and  the  resist-printed 
portion  another.  This  method  of  printing  is  anything  but 
new,  having  been  practised  as  long  ago  as  1845  when  the 
resist  consisted  of  a  mixture  of  rosin  and  tallow,  printed 


58    CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

on  the  silk  from  heated  rollers.  The  silk  was  then  dyed 
and  the  resist  subsequently  removed  by  treatment  with 
a  weak  alkaline  bath. 

DISCHARGE  OR  EXTRACT  PRINTING.  —  This  method  has 
for  its  foundation  the  fact  that  certain  colors  are  com- 
pletely dissipated  when  treated  with  reducing  agents  and 
subsequently  aged  to  prevent  the  return  of  the  color 
through  the  oxidizing  action  of  the  atmosphere.  The 
method  is  not  difficult  of  operation,  permitting  the  pro- 
duction of  a  design  in  pure  white  on  a  colored  ground  or 
"  blotch."  The  small  white  polka  dots  on  silks  are  pro- 
duced by  this  method.  The  large  ones  are  not,  being 
printed  on  by  means  of  zinc  white  in  gum  tragacanth.  To 
produce  the  small  white  dots,  a  color  thickener  is  mixed 
with  the  discharge  agent,  commonly  known  as  hydrosul- 
phite.  The  dots  are  printed  with  this  mixture  from  a 
suitably  engraved  roller.  A  certain  interval  is  permitted 
to  elapse  in  order  that  the  hydrosulphite  may  discharge 
the  ground-color  of  the  silk  and  the  piece  is  then  "aged" 
by  subjecting  it  to  superheated  steam.  To  guard  against 
return  of  temporarily  discharged  colors,  the  basic  dye- 
stuffs  are  as  a  rule  employed  for  the  ground-color  of  the 
silk. 

SILK  FINISHING.  —  This  branch  of  the  industry  has  for 
its  object  the  restoration  of  elasticity  to  the  woven  fiber, 
the  increase  of  luster  and  handle  or,  as  is  too  frequently 
the  case,  the  covering  over  of  defects  in  the  thread  or 
fabric. 

Silk  finishing  is  first  attempted  in  the  dye-house,  either 
through  the  use  of  the  emulsion  described  in  the  last 
chapter,  the  use  of  such  materials  as  diastofor  (a  concen- 
trated malt  preparation  valuable  for  its  content  of  diastase, 
the  fermentive  principle  of  malt),  which  serves  to  strengthen 
the  thread  temporarily  if  weakened  by  faulty  treatment  in 


SILK  PRINTING  AND  FINISHING  59 

dyeing,  or  by  the  metallicing  process  for  the  production 
of  extra  brilliance.  This  last  is  worthy  of  some  attention. 
The  dyed  silk,  still  damp,  is  placed  upon  a  buckling  appa- 
ratus and  stretched  as  it  dries  at  a  high  temperature.  The 
apparatus  is  so  devised  that  the  skeins  may  be  turned 
uniformly  as  they  receive  treatment.  This  treatment  is  at 
best  a  precarious  one.  As  has  been  previously  stated, 
stretching  the  silk  in  the  gum  before  stripping  is  produc- 
tive of  as  great  luster  and  one  of  greater  duration  without 
one  iota  of  the  risk  involved  in  metallicing.  On  the  other 
hand,  metallicing  has  the  advantage  in  that  it  lays  the 
fiber,  producing  a  better  looking  and  a  better  winding 
silk,  assuming,  of  course,  that  the  treatment  does  not 
overtax  the  thread,  which  is  a  matter  of  extreme  doubt. 
If  no  impurities  enter  the  thread  in  the  course  of  reeling 
and  throwing,  and  if  all  dyeing  operations  are  correctly 
carried  out  subsequently,  then  steam  stretching  in  the 
gum  yields  most  satisfactory  results  without  danger  to 
the  thread.  • 

FINISHING  MEDIA.  —  Certain  of  the  materials  employed 
as  color  thickeners  in  printing  are  applicable  as  finishing 
media.  Of  these,  gum  tragacanth  is  extensively  employed 
for  silk  finishing  in  combination  with  waxes.  Glue  and 
dextrine  are  also  commonly  used  for  finishing.  With  the 
exception  of  dextrine,  no  single  material  is  applied  to  the 
silk,  a  definite  combination  being  necessary  to  secure  the 
desired  result.  Glue  jelly  must  be  softened  with  soluble 
castor  oil.  Waxes  must  be  emulsified  with  alkali.  Ac- 
cording as  these  treatments  are  carefully  carried  out  or 
not,  so  will  the  silk  be  well  or  poorly  finished. 

The  extensive  use  of  glue,  coupled  with  the  fact  that 
glues  frequently  are  far  from  pure,  will  account  for  occa- 
sional defects  in  finished  silks  which  are  ascribed  to  the 
dyer's  carelessness.  The  writer  recalls  an  instance  where 


60    CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

broad  goods  that  had  been  dyed  the  shade  known  as 
" Alice  blue/'  some  months  after  weaving  developed  red 
spots  akin  to  those  that  result  from  mistakes  in  silk 
weighting,  and  accompanied  by  a  similar  tendering  of 
the  goods  wherever  the  spots  appeared.  Of  course,  the 
trouble  was  laid  to  the  dyer,  until  it  was  shown  that,  in 
finishing  the  silk,  a  glue  containing  an  excess  of  sulphurous 
acid  had  been  used  and  that  this  had  discharged  the  colors 
save  the  body  of  fast  red  which  is  very  difficult  to  dis- 
lodge. Hence  the  red  spots. 

The  glues  finding  the  greatest  favor  with  silk  finishers 
are  the  imported,  characterized  by  transparency  and  light 
color.  In  these  glues,  the  transparency  is  frequently 
accomplished  by  treating  the  glue  liquors,  in  the  course 
of  manufacture,  with  alum;  and  paleness  of  color  by  sub- 
sequently bleaching  the  liquors  with  sulphurous  acid  or 
its  derivatives.  Not  all  light  glues  are  so  bleached.  The 
higher  and  (hence)  more  expensive  grades  owe  their  pale- 
ness to  the  careful  selection  of  the  stock  from  which  they 
are  boiled.  It  is  to  the  finisher's  advantage  as  well  as 
the  manufacturer's,  to  keep  the  cost  of  his  materials  as 
low  as  possible.  Hence  the  possibility  of  defects  in  fin- 
ished silk  ensuing  from  impurities  in  the  finishing  media. 
These  may  not  be  due  to  the  glue  directly,  but  might  enter 
from  acidity  or  alkalinity  of  the  soluble  oils  used  for  soften- 
ing the  glue  jelly. 

THREAD  FINISHING. —  Although  this  method  was  origi- 
nally devised  in  order  that  the  manufacturer  might  impart 
certain  desirable  properties  to  the  thread  before  weaving, 
its  object  of  late  has  been  rather  to  gloss  over  defects  in 
the  initial  silk  fiber  or  ensuing  from  careless  handling  by 
the  dyer.  It  is  true  that  certain  finishing  media  applied 
to  the  dyed  thread  impart  remarkable  strength  thereto; 
but  this  is  only  temporary  at  best,  and  it  certainly  does 


SILK  PRINTING  AND  FINISHING  61 

not  follow  that  the  life  of  the  woven  silk  will  be  prolonged 
to  any  extent  thereby.  The  contrary  is  more  often  the 
case. 

In  thread  finishing,  the  silk  is  first  wound  from  the  skein 
onto  bobbins.  It  is  then  re-wound  from  these  upon  a 
second  set,  passing  meanwhile  through  a  bath  containing 
the  finishing  media,  then  through  a  series  of  brushes  which 
remove  any  excess  of  finish,  and  finally  over  a  heated  metal 
plate  which  dries  the  thread  ere  it  reaches  the  receiving 
bobbins.  Weak  threads  thus  treated  acquire  an  amazing 
strength  which  doubtless  renders  them  easy  of  warping 
and  weaving  where  they  otherwise  would  cause  consider- 
able trouble.  Unless,  however,  the  weighting  materials 
in  the  thread  so  treated  are  properly  combined,  this  heat- 
ing tends  to  upset  their  balance  so  that  the  silk  will  rot 
a  short  while  after  it  has  passed  the  looms. 

PIECE  FINISHING.  —  Successful  piece  finishing  is  as 
much  a  matter  of  adequate  machinery  as  of  media  em- 
ployed. Piece  goods  may  be  finished  without  the  use  of 
glue  or  gums,  etc.,  by  simply  passing  the  goods  through  a 
heated  copper  calender.  Again,  a  light  treatment  with 
dextrine  may  be  applied  and  the  goods  then  similarly 
calendered;  or  the  goods  may  receive  full  treatment  with 
softened  glue.  To  distinguish  between  goods  that  have 
been  finished  and  those  that  have  not,  it  is  necessary  to 
crumple  a  small  piece  in  the  hand  and  then  suddenly  re- 
lease it.  f  If  the  goods  have  been  finished,  they  will  spring 
out  into  shape;  if  not,  they  will  remain  crumpled,  t 

It  may  be  safely  asserted  that  where  all  other  processes* 
have  been  properly  carried  out,  little  danger  arises  from* 
the  practice  of  finishing  save  in  those  instances  where  the- 
finishing  media  are  impure. 


CHAPTER  VIII 
SILK   CONDITIONING 

CHEMICAL  ANALYSIS  VERSUS  CONDITIONING 

THE  rapid  growth  of  silk  conditioning  in  the  United 
States  during  the  past  few  years  renders  it  a  topic  worthy 
of  intimate  discussion.  The  movement,  on  the  whole,  is 
not  a  new  one.  As  early  as  1896  a  conditioning  house  was 
established  in  New  York.  Up  to  two  or  three  years  ago, 
its  services  were  not  in  noticeable  demand.  The  establish- 
ment, then,  of  a  rival  and  better  equipped  institution, 
vested  with  the  authority  of  the  Silk  Association  of  America, 
led  to  a  campaign  of  education  amongst  silk  manufacturers 
as  to  the  benefits  accruing  from  silk  conditioning  in  accord- 
ance with  European  practice. 

Too  much  credit  cannot  be  accorded  the  instigators  of 
any  movement  tending  to  reduce  an  industry  to  an  exact 
basis.  The  erstwhile  empiricism,  tantamount  to  a  condi- 
tion of  chaos,  characterizing  the  silk  industry,  certainly 
cried  for  reform.  It  is  a  curious  commentary,  however, 
that  American  industry  with  its  wide  latitude  for  the 
exercise  of  initiative  should,  because  of  the  false  premises 
assumed  by  those  desirous  of  bettering  existing  conditions, 
long  defer  the  adoption  of  remedial  procedure  only  to 
adopt,  in  the  end,  European  methods  which,  no  sooner  are 
they  adopted,  are  greatly  modified  or  even  discarded  by  our 
continental  contemporaries  themselves.  This  is  the  exact 
status  of  American  Silk  Conditioning. 

Lest  the  author  appear  unduly  prejudiced  in  favor  of 

62 


SILK  CONDITIONING  63 

his  own  system  of  silk  valuation,  he  hastens  to  avow  his 
recognition  of  the  considerable  good  thus  far  achieved  by 
conditioning.  In  so  far  as  mechanical  tests  are  concerned, 
the  system  is  practically  perfect.  For  determining  true 
invoice  weights,  it  is  practically  indispensable.  It  is  to  be 
noted,  however,  that,  apart  from  the  necessary  drying 
ovens  for  the  assay  of  this  last,  it  has  been  within  the  power 
of  every  manufacturer  for  years  past  to  determine  the 
count,  size,  and  twist  of  his  silk  with  accuracy  equal  to 
that  of  the  conditioning  house,  by  means  of  suitable 
apparatus  installed  in  his  own  mill.  A  certain  value,  how- 
ever, seems  to  attach  to  tests  conducted  under  a  separate 
roof  without  danger  of  bias. 

With  the  determination  of  the  true  conditioned  weight 
of  the  raw  silk,  the  usefulness  of  the  conditioning  house 
ends.  Great  stress,  indeed,  has  been  laid  upon  the  value 
of  the  " boil-off"  test,  as  a  panacea  for  all  silk  ills.  Un- 
fortunately, the  claims  made  for  this  test  are  but  illy 
founded.  It  is  a  reliable  check  for  the  throwster's  clear- 
ance, but  that  is  all.  The  contention  that  it  may  be  made 
the  basis  for  ordering  weighting  and  dyeing  is  absurd, 
despite  the  numerous  " statistics"  advanced  in  support 
of  the  theory.  Since  it  is  usually  at  the  weaver's  behest 
or,  at  best,  with  his  tacit  consent,  that  the  throwster  over- 
loads the  silk  with  soap  and  oil,  if  not  more  dangerous 
substances,  the  weaver's  subsequent  curiosity  to  discover 
if  clearance  has  been  put  in  is,  to  say  the  least,  ludicrous. 
It  is  a  waste  of  both  time  and  money  for  him  to  apply  to 
the  conditioning  house  for  this  information.  The  weaver 
is  concerned,  not  with  the  amount  of  clearance,  since  this 
costs  him  nothing,  but  with  the  nature  of  the  clearance 
which  may  prove  costly  in  the  end.  Conditioning  cannot 
supply  this  information.  Chemical  analysis  can. 

Unless  followed  by  chemical  analysis  of  the  silk,  condi- 


64    CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

tioning  house  boil-off  tests  are  worthless.  Says  Sig. 
Giuseppi  Corti,  of  the  Milan  Conditioning  House,  writing 
on  this  head  to  the  American  Silk  Journal : 

''Until  recently  the  boil-off  test,  as  made  uniformly  at 
all  conditioning  houses,  was  the  only  means  of  determining 
the  intrinsic  value  of  a  silk  as  well  as  the  amount  of 
weighting  it  had  received  during  reeling  or  throwing.  But 
appraising  the  value  of  silks  by  the  loss  in  boil-off,  having 
regard  only  to  the  amount  of  foreign  substances  they  may 
contain,  is  not  always  exact.  The  well-known  inequali- 
ties in  the  amount  of  pure  silk  fiber  found  in  the  same 
lot  of  silk  entirely  free  from  foreign  substances  make  it 
impossible  to  determine  with  exactitude  from  the  loss  of 
weight  in  boil-off  whether  it  was  weighted  when  in  the 
hands  of  the  throwster  and  to  what  extent. 

"Even  when  one  exercises  the  greatest  care  in  taking 
samples,  the  boil-off  tests  often  show  differences  of  from 
1  to  1.50%.  These  differences  sometimes  become  even 
more  marked  when  heavily  weighted  silks  are  being  tested 
because  of  the  volatilization  of  a  portion  of  the  overweight- 
ing during  conditioning.  It  is  only  when  the  raw  silk  is 
boiled  off  simultaneously  with  the  thrown  silk  that  the 
differences  between  the  results  obtained  represent  pretty 
nearly  the  amount  of  weighting  added  by  the  throwster. 

"On  account  of  these  different  causes  of  inequality  it 
has  sometimes  been  sought  to  prove  that  thrown  silks,  in 
which  a  light  weighting  had  been  introduced  to  facilitate 
the  winding,  would  lose  less  in  boil-off  than  the  corre- 
sponding raw  silk,  instead  of  showing  a  greater  loss. 

"From  the  above  the  necessity  of  having  recourse  to 
chemical  analysis  whenever  it  is  desired  to  determine  writh 
exactitude  the  weighting  of  a  raw  silk  is  most  evident.  The 
process  of  washing  with  distilled  water  heated  to  50°, 
which  is  still  used  in  some  silk  conditioning  houses,  is 


SILK  CONDITIONING  65 

certainly  an  improvement  over  the  boil-off  method,  but 
evidently  does  not  carry  with  it  the  guarantee  of  an  exact 
chemical  analysis,  because  if  the  weighting  is  composed 
of  substances  insoluble  in  water,  the  washing  will  some- 
times give  inexact  results. 

"The  Milan  Silk  Conditioning  House  (Societa  Anonima 
Co-operative  per  la  Stagionatura  e  FAssaggio  delle  sete 
ed  Affini  in  Milano)  realizing  the  great  value  of  the  method 
of  chemical  analysis  pursued  by  its  Laboratory  for  the 
Experimental  Study  of  Silk,  and  aiming  to  facilitate  the 
employment  of  methods  truly  scientific  in  place  of  those  in 
use  at  present,  has  decided  to  place  its  service  for  the  regu- 
lation of  the  purity  of  raw  silks  on  a  commercial  basis  by 
reducing  the  charge  for  analysis  to  four  francs  ($1.00) 
per  sample.'' 

So  long,  of  course,  as  the  silk  dyer  is  to  be  made  respon- 
sible for  defects  not  within  his  control,  the  present  system 
of  silk  valuation  will  suffice.  A  system  of  silk  valuation, 
however,  that  furnishes  absolutely  no  data  on  which  to 
base  the  ordering  of  dye-house  treatment  cannot  endure 
for  long.  As  a  practical  example  of  the  utter  futility  of 
conditioning  house  tests  with  respect  to  this  latter  con- 
tingency, let  us  consider  the  following. 

Since  the  early  eighties,  fat  has  been  used  for  adultera- 
tion of  raw  silk,  rendering  degumming  very  difficult.  In 
Italy  there  has  long  been  employed,  for  this  purpose,  a 
mixture  consisting  of  salt,  soap,  unsaponified  grease,  min- 
eral oil  and  gelatine  —  a  compound  containing  the  organic 
elements  of  silk  itself  and  which  increases  its  weight  but 
not  its  volume  or  strength. 

We  shall  assume  that  silk,  so  adulterated,  has  been  pur- 
chased by  the  manufacturer,  who  sends  it  to  the  condition- 
ing house  for  assay.  Note  that,  in  this  instance,  the 
figure  for  conditioned  weight  obtained  by  drying  the  silk 


66    CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

and  adding  11  %  for  average  moisture  in  no  sense  repre- 
sents the  true  silk  in  the  shipment.  The  silk  is  now  sub- 
jected to  the  boil-off  test.  Since  the  character  of  the 
adulteration  precludes  the  normal  degumming  of  the  silk, 
very  little  gum  comes  off,  with  a  result  that  the  condition- 
ing house  certificate  mill  indicate  that  this  is  a  low-boiling 
silk  and  hence  one  of  good  quality !  Let  us  go  a  step  further 
and  assume  that  the  silk  is  now  thrown  and  returned  for 
boil-off  to  the  conditioning  house.  The  test  will  simply 
show  that  additional  soap  and  oil  has  been  put  in  by  the 
throwster.  Since  the  manufacturer  orders  this  done,  the 
result  of  the  test  must  be  of  considerable  comfort  to  him! 
Let  the  reader  carefully  observe,  however,  that  at  no  time 
have  the  tests  revealed  the  presence  of  the  dangerous 
ingredients  in  the  silk.  The  silk  now  goes  to  the  dyer.  It 
contaminates  his  boiled-off  liquor.  Once  in  the  tin  bath, 
the  fats  remaining  in  the  silk  combine  with  the  former  to 
form  metallic  insoluble  soaps.  These  prevent  even  dyeing; 
create  chalkiness  of  the  thread  and  weaken  it,  and  the  dyer, 
in  order  to  produce  anything  like  a  normal  result,  must 
subject  this  silk  to  abnormally  drastic  treatments  through- 
out, so  that  by  the  time  the  silk  has  passed  the  looms  it  is 
short-lived.  Now,  what  has  conditioning  availed  the  owner 
of  this  silk?  The  sellers,  aware  of  its  questionable  charac- 
ter, doubtless  secretly  congratulate  themselves  on  not  only 
the  impossibility  of  detection  by  conditioning  house  tests, 
but  also  on  the  fact  that  the  very  figure  for  conditioned 
weight  is  fallacious!  And  since  the  bulk  of  raw  silk 
coming  to  the  American  market  is  more  or  less  adulter- 
ated, just  what  is  gained  by  conditioning  tests?  What 
shall  it  avail  a  manufacturer  to  know  the  exact  size, 
twist,  or  count  of  his  silk,  to  be  told  that  the  throwster 
has  done  just  what  he  has  ordered  him  to  do  and  yet 
remain  in  utter  ignorance  of  those  factors  upon  which 


SILK  CONDITIONING  67 

depend  the  success  of  dyeing  operations  and  the  life  of 
the  woven  silk? 

Since  certain  standard  methods  obtain  for  the  treat- 
ment of  silk  in  the  dye-house,  the  manufacturer  is  con- 
cerned solely  with  the  question  whether  the  raw  silk  he 
purchases  is  in  a  fit  state  to  go  to  the  dyer  and  be  returned 
in  good  condition,  after  throwing.  Once  he  determines  to 
have  his  raw  silk  regularly  assayed,  his  thrown  silk  exam- 
ined, he  is  then  in  a  position  to  determine  the  exact  degree 
of  the  dyer's  responsibility.  How  can  he  justly  declare 
that  defects  in  the  dyed  silk  are  due  to  the  dyer's  careless- 
ness unless  he  has  previously  determined  whether  or  not 
the  thrown  silk  contained  impurities  which  interfered  with 
dyeing  processes?  Again,  why  should  he  accuse  the 
throwster  of  malpractice  unless  he  is  confident  beyond 
perad venture  of  doubt  that  the  raw  silk  was  pure?  By 
all  means  let  him  avail  himself  of  means  preventive  of  his 
purchasing  excess  moisture.  Let  him  surround  himself 
with  every  system  that  safeguards  his  finances  and  pro- 
tects his  profit ;  but  let  him  apply  an  equal  measure  of 
common  sense  to  the  treatment  of  his  raw  material  at  its 
most  important  stage! 

A  rational  system  of  silk  valuation  presupposes  the 
following: 

1.  The  determination  of  the  conditioned  weight;  i.e., 
absolute  dry  weight  plus  11  %. 

2.  The  complete  chemical  analysis  of  the  raw  silk. 

3.  The  complete  chemical  analysis  of  the  thrown  silk. 

4.  The  complete  chemical  analysis  of  the  dyed  silk. 
The  first  is  indispensable  to  the  proper  checking  of  raw 

silk  invoices. 

The  second  is  a  prerequisite  to  the  ordering  of  all  sub- 
sequent treatments  of  the  silk.  If  the  raw  silk  is  found  to 
be  free  of  adulteration,  then,  — 


68    CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

The  third  serves  as  an  absolute  check  on  the  work  of  the 
throwster.  No  insoluble  materials  employed  to  obtain 
factitious  clearance  can  escape  detection. 

The  raw  and  thrown  silks  found  to  be  normal,  responsi- 
bility for  the  quality  of  the  silk  now  rests  with  the  dyer. 
The  amount  of  weighting  can  now  be  rationally  ordered  and 
the  analysis  of  the  dyed  silk  checks  not  only  the  amount 
of  weighting  but  the  character  as  well.  In  this  way  it  is 
possible  to  forecast,  within  close  limits,  the  life  of  the  woven 
silk  before  the  dyed  silk  has  passed  through  the  looms,  i.e., 
at  a  time  when  a  claim  against  the  dyer,  for  mistakes  on  his 
part,  may  be  safely  prosecuted.  The  substantiation  of  such 
cases  must,  however,  rest  upon  tJie  certain  knowledge  that  the 
silk  contained  no  abnormal  ingredients  before  it  reached  the 
dyer. 

Any  other  system  of  silk  valuation  must  fail  of  adequate 
protection  to  the  manufacturer.  It  is  unsafe  for  him  to 
take  constant  refuge  behind  the  legal  maxim  "caveat 
emptor";  for  while  the  law  does  distinguish  between  vis- 
ible and  latent  defects,  the  defects  in  silk  are  easily  proven 
to  be  latent,  and  for  him  who  shall  take  the  initiative  in 
litigation  involving  the  quality  of  silk  exists  the  possibility 
of  mulcting  the  manufacturer  of  heavy  damages. 


APPENDIX 

INFLUENCE    OF    PRIOR    PROCESSES    ON    WINDING    AND 

WEAVING 

THAT  silk  which  winds  well  is  readily  warped  and  woven 
is  virtually  an  axiom.  Silk  winding  is  the  bete  noir  of 
the  manufacturer,  and  responsibility  for  the  difficulties  he 
experiences  at  this  stage  is  invariably  laid  at  the  dyer's 
door,  frequently  with  justice  although  not  always  so. 

It  is  worthy  of  notice  that  concerns  operating  their 
own  dye-houses  do  not  suffer  the  inconveniences  of  poor- 
winding  silk  as  frequently  as  those  who  are  dependent 
upon  the  commission  dyer.  This  would,  at  first  blush, 
appear  to  prove  the  thesis  that  the  dyer  is  responsible 
for  the  winding  qualities  of  the  silk.  Let  us  subject  the 
matter  to  a  little  closer  scrutiny,  lest  we  form  an  erroneous 
opinion.  Conditions  prevailing  in  mill  dye-houses  differ 
radically  from  those  obtaining  in  commission  dye-houses. 
The  silk  run  in  the  former  is  usually  of  good  quality.  Much 
of  the  silk  treated  in  the  latter  is  inferior  if  not  altogether 
worthless.  The  weighting  demanded  by  manufacturers 
equipped  with  dyeing  facilities  is  always  kept  within 
rational  limits ;  the  weighting  demanded  of  the  commis- 
sion dyer  is  frequently  so  far  in  excess  of  what  the  silk  can 
normally  stand  and  the  dyer  is  so  often  forced  to  subject 
the  silk  to  many  unusual  processes  that  it  is  small  wonder 
that  difficulty  is  subsequently  experienced  in  winding. 

Poor  winding  is  due  either  to  stickiness,  tenderness  of 
the  thread  or  its  brittleness.  It  is  necessary  to  distinguish 

69 


70    CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

carefully   between   these   defects.    All   may   be   brought 
about  through  the  following  errors  on  the  dyer's  part: 

1.  Over-stripping  the  silk  (stickiness). 

2.  Insufficient  washing  after  stripping  (stickiness). 

3.  The  use  of  oxidized  tin  liquors  (tenderness). 

4.  Insufficient  washing  after  phosphate  (stickiness). 

5.  The  use  of  "  broken  "  silicate  baths  (brittleness). 

6.  An  excess  of  casein  in  the  phosphate  (stickiness). 

7.  The  use  of  zinc  chloride  after  phosphate  (tenderness). 

8.  The  use  of  hard  water  after  certain  baths  (brittleness). 
All  of  these  conduce  to  the  bad  winding  of  the  silk. 

Some,  in  addition,  are  responsible  for  loss  of  luster. 

The  reader  must  bear  in  mind,  however,  that  initial  adulter- 
ations in  raw  and  thrown  silk  are  as  likely  to  create  tJw  above 
defects  after  silk  has  been  weighted  and  dyed  as  any  careless- 
ness on  the  dyer's  part. 

Effect  of  Moisture  on  Weaving  —  Humidification 

Recent  developments  in  the  humidification  of  weave- 
sheds,  with  a  view  to  the  elimination  of  the  frictional  elec- 
tricity of  yarns,  claim  the  interest  of  the  investigator. 
Numerous  "  systems  "  of  humidifying  have  come  into  the 
market.  From  a  comparatively  simple  matter,  the  move- 
ment has  assumed  complex  proportions  involving,  at  this 
writing,  such  features  as  the  removal  of  disease  germs! 

A  word  or  two  of  comment  may  not  be  altogether  irrele- 
vant. In  the  first  place,  the  apparatus,  as  now  put  on  the 
market,  is  in  every  instance  unnecessarily  elaborate.  One 
of  the  most  successful  "  systems "  coming  within  the 
observation  of  the  writer  consists  of  a  pipe  which  inducts 
exhaust  steam  into  a  corner  of  the  weaving  room,  which 
pipe  is  backed  by  a  small  fan.  Simple  as  this  seems,  it 
accomplishes  all  that  can  possibly  be  required  in  the  way 
of  humidification. 


APPENDIX  71 

It  is,  indeed,  questionable  if  anything  elaborate  in  the 
way  of  "  humidifying  "  is  required  in  the  case  of  silk  weav- 
ing. True,  it  is  desirable  that  the  humidity  of  the  room  in 
which  the  looms  are  installed  shall  be  as  nearly  constant 
as  possible  throughout  the  year.  It  is  not  to  be  denied 
that  moisture  has  a  definite  effect  upon  the  facility  with 
which  certain  yarns  are  woven.  In  the  case  of  silk,  how- 
ever, it  is  extremely  doubtful  if  the  effect  is  genuinely 
advantageous. 

Silk  is  practically  the  most  hygroscopic  of  textile  fibers. 
Rational  treatment,  in  the  way  of  weighting,  does  not 
reduce  its  hygroscopicity.  Properly  treated  silks  have 
woven  well,  without  humidification,  since  time  imme- 
morial. On  the  other  hand,  where  silk  is  workable  only 
with  difficulty,  it  is  usually  due  to  innate  defects  or  defec- 
tive dyeing  treatment  in  which  latter  event  the  subjection 
of  the  silk  to  excess  moisture  so  far  from  permanently 
overcoming  these  defects  is  positively  harmful  in  that  it 
still  further  dissociates  illy-combined  weighting  ingredients 
within  the  fiber  and  practically  insures  the  rapid  dissolu- 
tion of  the  silk. 

Viewed  exclusively  from  the  commercial  standpoint, 
whenever  a  silk  manufacturer  installs  a  system  of  humidi- 
fying, he  gives  his  dyer  an  advantage  over  him.  Silks 
which  would  wind  poorly  because  of  brittleness  or  other 
defects,  now  have  their  elasticity  temporarily  augmented 
with  a  result  that  they  will  pass  the  looms  unchecked. 
Since  the  manufacturer  is  responsible  financially  for  the 
quality  of  the  silk  he  weaves,  this  phase  of  the  question 
becomes  worthy  of  his  serious  consideration.  It  were 
safer  for  him  to  dispense  with  what  is  at  best  a  temporary 
fad  in  favor  of  the  rational  examination  of  his  raw  and 
dyed  silks  thereby  affording  himself  unlimited  protection 
with  reference  to  the  above-cited  contingency. 


72    CHEMICAL   ASPECTS  OF  SILK  MANUFACTURE 

CLASSIFICATION  OF  RAW  SILKS 
Adopted  by  Division  A,  June  15,  1908. 

At  the  request  of  the  Board  of  Managers  of  the  Silk 
Association  of  America,  Division  A.  has  carefully  considered 
the  classification  names  to  apply  to  the  various  qualities 
of  European  Silk  and  Japan  Filatures,  Re-reels  and  Kake- 
das  dealt  in  on  the  New  York  market  and  have  adopted 
the  following: 

EUROPEAN  SILKS 

Grand  Extra Best  No.  1 

Extra  Classical No.  1 

Best  Classical Realina 

Classical 

JAPAN  SILKS 

FILATURES  RE-REELS 

Double  Extra Extra 

Extra No.  1 

Sinshlu  Extra No.  1-1£ 

Best  No.  1  to  Extra No.  U 

Best  No.  1 No.  lf-2 

Hard  Nature  No.  1 No.  2 

No.  1,  of  the  grade  of No.  2-2^ 

Sinshiu  Okaya  (Chicken) No.  2^ 

Summer  reeling  Season  1908-9 No.  3 

KAKEDA 

No.  1-U Best  Extra 

No.  U Extra 

No.  H-2 No.  1 

No.  2 No.  2 

No.  3 

The  Board  of  Managers  of  the  Silk  Association  of  America 
at  a  meeting  on  June  10,  1908,  approved  the  foregoing 
classification  with  the  recommendation  that  the  Raw  Silk 
Division  of  the  Association  consider  the  feasibility  of 


APPENDIX  73 

tabulating  a  set  of  descriptions  with  samples  of  raw  silk 
to  represent  the  agreed-upon  classification  at  the  opening 
of  each  silk  season. 

On  June  15,  1908,  the  Raw  Silk  Division  voted  to  en- 
deavor to  adopt  a  standard  for  No  1  filatures  and  re-reels 
as  soon  after  the  opening  of  each  silk  season  as  sufficient 
silk  shall  have  arrived  in  New  York  to  give  a  fair  repre- 
sentation of  the  average  quality  of  the  season's  summer 
reelings,  and  this  matter  is  now  under  consideration  by 
them. 

It  is  believed  that  the  deposit  with  the  Silk  Association 
of  America  at  the  opening  of  each  silk  season  of  a  set  of 
samples  representing  say  five  grades  of  silk  would  bring 
within  the  reach  of  both  buyer  and  seller  a  standard  to 
which  offerings  of  parcels  could  be  compared;  thereby 
avoiding  existing  uncertainty  and  misapprehension  as  to 
qualities. 

CUSTOMS    PREVAILING    IN    THE    SKEIN    SILK    DYEING 
TRADE  OF  THE  UNITED  STATES.1 

Storage  and  Insurance 

The  dyer  provides  safe  and  suitable  storage  for  silk  sent 
to  him  to  dye,  without  charge  to  the  customer,  assumes 
liability  for  the  loss,  theft,  or  destruction  of  silk  while  in 
his  possession,  and  keeps  it  fully  insured. 

Transportation  Charges 

The  dyer  pays  the  transportation  charges  on  the  silk 
sent  him  to  dye,  unless  otherwise  agreed,  and  he  delivers 
the  dyed  silk  free  within  a  short  radius  of  his  dye-house. 
Transportation  charges  on  dyed  silk,  shipped  to  a  consider- 
able distance,  to  be  paid  by  the  customer. 

1  Quoted  from  "The  Value  of  Conditioning." 


74    CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

Packing 

The  dyer  when  shipping  the  dyed  silk  is  to  have  it  safely 
and  suitably  packed,  using  such  quality  of  paper,  cords, 
and  bagging  as  will  insure  the  proper  protection  of  the  silk. 

Withdrawals  of  Undyed  Silk 

Should  the  customer  order  silk  to  be  sent  by  the  dyer  to 
some  other  dye-house,  or  to  be  returned  to  him  undyed, 
he  must  reimburse  the  dyer  for  any  money  that  has  been 
expended  by  him  for  transportation  charge,  insurance,  or 
storage  of  such  silk. 

Time  of  Delivery  of  Order 

Dyer  must  execute  order  with  reasonable  promptness. 
If  silk  is  on  hand  at  the  dyer's,  shipment  back  of  the  dyed 
silk  may  be  expected  in  from  one  to  three  weeks  (accord- 
ing to  circumstances  and  the  nature  of  the  work)  from 
receipt  of  the  order. 

Prices,  Discounts  and  Terms 

Prices,  discounts,  and  terms,  are  matters  of  mutual 
arrangement.  A  standard  printed  price-list  is  generally 
used  as  a  basis  for  prices.  Bills  are  rendered  at  the  end  of 
each  month,  a  common  basis  of  settlement  being  cash 
within  30  days. 

Orders  for  Weighting 

The  dyer  is  obligated  to  deliver  silk  within  the  limits 
of  the  weighting  ordered.  Thus,  20—22  oz.  is  supposed 
not  to  run  below  20  oz.  and,  unless  by  special  agreement, 
a  greater  weight  than  22  oz.  cannot  be  claimed.  If  the 
weight  comes  less  than  20  oz.  the  customer  can  claim  the 


APPENDIX  75 

price  corresponding  with  what  it  weighs.  If,  however, 
it  runs  over  22  oz.,  even  when  not  specially  agreed  on,  the 
dyer  cannot  charge  more  for  the  extra  weight. 

Weighting  of  Silks  with  Varying  Boil-offs 

Whether  the  dyer  treats  silk  having  either  a  light  or  a 
heavy  boil-off,  his  price  is  the  same. 

Matching  Colors 

The  dyer  does  not  undertake  to  guarantee  an  exact 
match  to  sample,  but  does  undertake  to  furnish  a  com- 
mercial match,  that  is,  a  shade  so  close  that  fabrics  made 
of  it  can  be  properly  delivered  as  that  color.  If  the  cus- 
tomer finds  on  examination  of  dyed  silk  that  same  is  off 
shade,  or  too  dark,  or  too  light,  the  dyer  will  make  the 
necessary  modification  of  the  color,  if  it  can  be  done  without 
injury  to  the  working  qualities  of  the  silk,  without  extra 
charge. 

If,  through  his  error,  the  dyer  puts  on  the  silk  the  wrong 
color  or  weighting,  the  customer  may  use  the  lot  if  he 
chooses  to  do  so  to  the  best  advantage,  charging  the  dyer 
the  loss,  if  any.  If  this  is  impossible  the  dyer  may  be 
required  to  pay  for  the  silk  at  current  market  prices. 

Shady  Silk 

Should  silk  be  found  to  be  shady  to  an  uncommercial 
degree  and  the  defect  be  found  not  due  to  the  nature  of 
the  silk  the  dyer  must  try  and  rectify  the  trouble  at  his 
own  expense,  and  should  this  be  impossible  he  may  be 
required  to  keep  and  pay  for  the  lot. 

Should  the  customer,  before  knowing  of  the  trouble, 
have  put  such  silk  in  work  the  dyer  may  not  only  be  re- 
quired to  make  right,  or  to  take  back  and  pay  for,  the  silk, 


76    CHEMICAL  ASPECTS  OF  SILK  MANUFACTURE 

as  already  stated,  but  he  should  reimburse  the  customer 
for  money  actually  spent  in  the  winding,  warping,  quilling, 
etc.,  of  such  defective  lot. 

He  is  not,  however,  to  be  held  liable  for  damaged  cloth, 
woven  from  such  material,  past  the  point  where  the  defect 
should  have  become  apparent,  as  the  weaving  of  visibly 
imperfect  goods  should  not  be  proceeded  with. 

The  consequential  damages  in  such  cases  due  to  standing 
looms,  goods  late  for  delivery,  etc.,  fall  upon  the  customer. 

Rotten  Silk 

Should  silk,  originally  sound,  be  returned  from  the 
dyer  rotten,  or  seriously  defective  in  strength,  or  should 
it  while  remaining  in  stock  for  a  reasonable  time  after 
dyeing,  and  under  proper  conditions  of  storage,  develop 
such  trouble,  the  dyer  can  be  called  on  to  take  back  and 
pay  for  the  silk. 

If,  however,  the  weighting  ordered  is  beyond  the  bounds 
of  prudence  and  the  limitations  of  good  practice,  the 
dyer  should  promptly  notify  the  customer  to  that  effect, 
before  proceeding  with  the  order,  and  should  the  customer 
then  direct  that  the  work  be  proceeded  with,  any  loss 
that  may  arise  if  the  silk  turns  out  unsound  must  be  borne 
by  the  owner. 

Fast  Colors 

Dyers  are  supposed  to  make  their  colors  commercially 
fast  for  such  ordinary  purposes  as  the  goods  are  used  for. 
Customers  wanting  colors  fast,  i.e.,  not  liable  to  change 
by  light,  washing,  perspiration,  or  what  not,  must  so  specify 
in  ordering,  and  charge  for  the  work  is  made  accordingly. 

If  the  silk  is  ordered  "  fast  "  for  certain  uses,  and  is 
paid  for  on  that  basis,  and  claims  should  come  upon  the 


APPENDIX  77 

manufacturer  for  a  deficiency  in  this  report  when  the  fabric 
has  been  used  under  reasonable  conditions,  the  dyer  may 
properly  be  called  on  to  make  good  such  claims  as  the 
manufacturer  has  had  to  allow. 

Mixed  Silk 

Should  the  dyer  mix  one  customer's  silk  with  another's, 
or  different  lots  of  the  same  customer's  silk,  he  is  charge- 
able with  the  loss  that  may  result. 

Bad  Winding 

When  properly  thrown  silk  is  so  handled  in  the  dyeing 
that  it  is  difficult  to  wind,  and  when  in  consequence  the 
customer  has  to  pay  extra  wages  for  the  winding  of  it, 
and  when  excessive  waste  may  be  caused  thereby,  such 
loss  in  wages  and  waste  is  properly  chargeable  to  the  dyer. 

As  souple  dyed  silks  generally  wind  poorly,  specific 
arrangement  with  dyer  should  be  made  regarding  same. 


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